Added migration page overview

pages/specification/migration/_index.md

@@ -3,5 +3,78 @@ title: Migrating from older drafts
 section: docs
 ---
 
-The release notes discuss the changes impacting users and implementers:
+### Introduction
 
+Just as your schemas evolve over time, the JSON Schema specification does as well. This guide provides useful information to make upgrading your schemas across versions of the specification a breeze.
+
+Learn how to use our migration guides and tooling ([AlterSchema](https://alterschema.sourcemeta.com/)) to bring your work with you.
+
+### Keywords Overview
+
+Here is a comprehensive overview to get you going.
+
+| All Keywords            | Specification | Draft introduction | Removed | Changed                        |
+| ----------------------- | ------------- | ------------------ | ------- | ------------------------------ |
+| `$anchor`               | Core          | 2019-09            | No      | No (updated in 2020)           |
+| `$comment`              | Core          | 07                 | Yes     | -                              |
+| `$id`                   | Core          | 06                 | No      | Replaced `id`                  |
+| `$defs`                 | Core          | 2019-09            | No      | Replaced `definitions`         |
+| `$dynamicAnchor`        | Core          | 2020-12            | No      | Replaced `$recursiveAnchor`    |
+| `$dynamicRef`           | Core          | 2020-12            | No      | Replaced `$recursiveRef`       |
+| `$recursiveAnchor`      | Core          | 2019-09            | No      | Replaced by `$dynamicAnchor`   |
+| `$recursiveRef`         | Core          | 2019-09            | No      | Replaced by `$dynamicRef`      |
+| `$ref`                  | Core          | 2019-09            | No      | No                             |
+| `$schema`               | Core          | 02                 | No      | No                             |
+| `$vocabualry`           | Core          | 2019-09            | No      | No                             |
+| `additionalItems`       | Core          | 03                 | No      | No                             |
+| `allOf`                 | Core          | 04                 | No      | No                             |
+| `anyOf`                 | Core          | 04                 | No      | No                             |
+| `const`                 | Validation    | 06                 | No      | No                             |
+| `contains`              | Core          | 06                 | No      | No                             |
+| `contentEncoding`       | Validation    | 07                 | No      | No                             |
+| `contentMediaType`      | Validation    | 07                 | No      | No                             |
+| `contentSchema`         | Validation    | 2019-09            | No      | No                             |
+| `definitions`           | Validation    | 04                 | No      | Replaced by` $defs`            |
+| `default`               | Validation    | 01                 | No      | No                             |
+| `dependencies`          | Core          | 03                 | No      | No                             |
+| `dependentRequired`     | Validation    | 2019-09            | No      | No                             |
+| `dependentSchemas`      | Core          | 2019-09            | No      | Replaced `dependencies`        |
+| `deprecated`            | Validation    | 2019-09            | No      | No                             |
+| `disallow`              | Validation    | 03                 | Yes     | No                             |
+| `divisibleBy`           | Validation    | 02                 | No      | Replaced by `multipleOf`       |
+| `else`                  | Core          | 07                 | No      | No                             |
+| `enum`                  | Validation    | 01                 | No      | No                             |
+| `examples`              | Validation    | 06                 | No      | No                             |
+| `exclusiveMaximum`      | Validation    | 03                 | No      | Replaced `maximumCanEqual`     |
+| `exclusiveMinimum`      | Validation    | 03                 | No      | Replaced `minimumCanEqual`     |
+| `extends`               | Validation    | 03                 | Yes     | No                             |
+| `format`                | Validation    | 02                 | No      | -                              |
+| `id`                    | Core          | 04                 | No      | Replaced by `$id`              |
+| `if`                    | Core          | 07                 | No      | No                             |
+| `items`                 | Core          | 2019-09            | No      | Replaced by `prefixItems`      |
+| `maxContains`           | Validation    | 2019-09            | No      | No                             |
+| `maxProperties`         | Validation    | 04                 | No      | No                             |
+| `maximumCanEqual`       | Validation    | 02                 | No      | Replaced by `exclusiveMaximum` |
+| `minimumCanEqual`       | Validation    | 02                 | No      | Replaced by `exclusiveMinimum` |
+| `minContains`           | Validation    | 2019-09            | No      | No                             |
+| `minProperties`         | Validation    | 04                 | No      | No                             |
+| `multipleOf`            | Validation    | 04                 | No      | Replaced `divisibleBy`         |
+| `not`                   | Core          | 04                 | No      | No                             |
+| `oneOf`                 | Core          | 04                 | No      | No                             |
+| `optional`              | Validation    | 02                 | No      | Replaced by `required`         |
+| `pattern`               | Core          | 03                 | No      | No                             |
+| `patternProperties`     | Core          | 03                 | No      | No                             |
+| `prefixItems`           | Core          | 2020-12            | No      | Replaced `items`               |
+| `propertyNames`         | Core          | 06                 | No      | No                             |
+| `readOnly`              | Validation    | 07                 | No      | No                             |
+| `required`              | Validation    | 03                 | No      | No                             |
+| `requires`              | Validation    | 02                 | Yes     | -                              |
+| `title`                 | Validation    | 01                 | No      | No                             |
+| `then`                  | Core          | 07                 | No      | No                             |
+| `type`                  | Validation    | 02                 | No      | No                             |
+| `unevaluatedItems`      | Core          | 2019-09            | No      | No                             |
+| `unevaluatedProperties` | Core          | 2019-09            | No      | No                             |
+| `uniqueItems`           | Assertion     | 02                 | Yes     | No                             |
+| `writeOnly`             | Validation    | 07                 | No      | No                             |
+
+For a detailed read-through about all the changes see each Draft migration guide.