Added README

Author: RunDevelopment

README.md

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+# RegExp AST analysis
+
+[![Actions Status](https://github.com/RunDevelopment/regexp-ast-analysis/workflows/Node.js%20CI/badge.svg)](https://github.com/RunDevelopment/regexp-ast-analysis/actions)
+[![npm](https://img.shields.io/npm/v/regexp-ast-analysis)](https://www.npmjs.com/package/regexp-ast-analysis)
+
+This is a library providing functionalities to analyse [JavaScript RegExp](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/RegExp).
+
+All functions operate on AST nodes produced by [regexpp](https://github.com/mysticatea/regexpp). Characters are parsed by [refa](https://github.com/RunDevelopment/refa).
+
+## Usage
+
+Install the library using npm:
+
+```bash
+npm i regexp-ast-analysis
+```
+
+Import the library:
+
+```js
+import * as RAA from "regexp-ast-analysis";
+```
+
+## Documentation
+
+Links to the full API documentation:
+
+- [Latest release](https://rundevelopment.github.io/regexp-ast-analysis/docs/latest/)
+- [Development](https://rundevelopment.github.io/regexp-ast-analysis/docs/dev/)