document extension workaround for other bundlers (#195)

Author: tatethurston

CHANGELOG.md

@@ -8,6 +8,7 @@
 
 - Fix JSON deserialization. #181 introduced a regression that caused TwirpScript servers' JSON serialization to fail.
 - Distribute strict ESM. A CommonJS is runtime is included for legacy node clients. Code generation uses ESM and requires Node.js v14 or later.
+  If you're using a compiler other than TypeScript such as `webpack`, please see [these instructions](https://github.com/tatethurston/TwirpScript#webpack-setup)
 - Use [ProtoScript](https://github.com/tatethurston/ProtoScript) code generation. This will result in some generated imports coming from `protoscript` instead of `twirpscript`, but this is a non breaking change. These imports were previously delegated to ProtoScript via reexports inside TwirpScript, and that indirection has now been removed.
 
 ## v0.0.60

README.md

@@ -56,6 +56,7 @@ TwirpScript implements the latest [Twirp Wire Protocol (v7)](https://twitchtv.gi
 - [Working with other tools](#working-with-other-tools)
 - [Caveats, Warnings and Issues ⚠️](#caveats-warnings-and-issues-%EF%B8%8F)
 - [FAQ](#faq)
+- [Webpack Setup](#webpack-setup)
 - [Contributing 👫](#contributing-)
 - [Licensing 📃](#licensing-)
 
@@ -99,6 +100,7 @@ To learn more about the motivation behind Twirp (and a comparison to REST APIs a
 
 - Node.js v16 or greater
 - TypeScript v4.7 or greater when using TypeScript
+- [webpack setup](#webpack-setup) when using a compiler other than TypeScript (like webpack)
 
 ## Getting Started
 
@@ -848,6 +850,33 @@ gRPC is great, but has a large runtime (and corresponding complexity) that is un
 
 To learn more about the motivation behind Twirp (and a comparison to REST APIs and gRPC), check out the [announcement blog](https://blog.twitch.tv/en/2018/01/16/twirp-a-sweet-new-rpc-framework-for-go-5f2febbf35f/).
 
+## Webpack Setup
+
+If you're using a compiler other than TypeScript, such as webpack, this [outstanding issue in TypeScript](https://github.com/microsoft/typescript/issues/37582) adds an additional hurdle.
+
+The short summary of the issue:
+
+- Extensions are required for ESM imports.
+- Extension-less imports have sidestepped this TypeScript issue, but extensions are required for ESM adoption.
+- The TypeScript compiler requires `.js` extensions for imports.
+- Compilers other than TypeScript expect `.ts` extensions for imports.
+
+The TypeScript team is investigating [improving this issue](https://github.com/microsoft/TypeScript/issues/37582) in their [4.9 plan](https://github.com/microsoft/TypeScript/issues/50457)
+
+Webpack users can use [extensionAlias](https://webpack.js.org/configuration/resolve/#resolveextensionalias) to solve this problem:
+
+```diff
+module.exports = {
++  resolve: {
++    extensionAlias: {
++      ".js": [".ts", ".js"],
++    },
++  },
+};
+```
+
+For more context, see [TypeScript#37582](https://github.com/microsoft/typescript/issues/37582) and [Webpack#13252](https://github.com/webpack/webpack/issues/13252).
+
 ## Contributing 👫
 
 PR's and issues welcomed! For more guidance check out [CONTRIBUTING.md](https://github.com/tatethurston/twirpscript/blob/main/CONTRIBUTING.md)