feat: implement hot module replacement middleware

.github/workflows/nodejs.yml

@@ -5,10 +5,12 @@ on:
     branches:
       - main
       - next
+      - hot-middleware
   pull_request:
     branches:
       - main
       - next
+      - hot-middleware
 
 permissions:
   contents: read

README.md

@@ -79,6 +79,7 @@ See [below](#other-servers) for an example of use with fastify.
 |        **[`writeToDisk`](#writetodisk)**        |        `boolean\|Function`        |                    `false`                    | Instructs the module to write files to the configured location on disk as specified in your `webpack` configuration. |
 |   **[`outputFileSystem`](#outputfilesystem)**   |             `Object`              | [`memfs`](https://github.com/streamich/memfs) | Set the default file system which will be used by webpack as primary destination of generated files.                 |
 | **[`modifyResponseData`](#modifyresponsedata)** |            `Function`             |                  `undefined`                  | Allows to set up a callback to change the response data.                                                             |
+|                **[`hot`](#hot)**                |         `boolean\|Object`         |                  `undefined`                  | Enables a Server-Sent Events endpoint that drives the browser HMR client.                                            |
 |       **[`forwardError`](#forwarderror)**       |             `boolean`             |                    `false`                    | Enable or disable forwarding errors to the next middleware.                                                          |
 
 The middleware accepts an `options` Object. The following is a property reference for the Object.
@@ -312,6 +313,51 @@ middleware(compiler, {
 });
 ```
 
+### hot
+
+Type: `Boolean | Object`
+Default: `undefined`
+
+Enables hot module replacement by serving a [Server-Sent Events](https://developer.mozilla.org/en-US/docs/Web/API/Server-sent_events) endpoint that publishes the webpack compiler's `building`, `built` and `sync` events to connected clients. When `true`, defaults are used; pass an object to customise. Use this option together with the browser runtime shipped as `webpack-dev-middleware/client`.
+
+```js
+const webpack = require("webpack");
+
+const compiler = webpack({
+  /* Webpack configuration with HotModuleReplacementPlugin and the client entry */
+});
+
+middleware(compiler, { hot: true });
+```
+
+#### `hot.path`
+
+Type: `String`
+Default: `'/__webpack_hmr'`
+
+Path the SSE endpoint is served at. Must match the `path` option used by the client.
+
+#### `hot.heartbeat`
+
+Type: `Number`
+Default: `10000`
+
+Heartbeat interval (in milliseconds) used to keep the SSE connection alive when no compilation events are produced.
+
+#### `hot.log`
+
+Type: `Function | false`
+Default: the dev middleware's infrastructure logger
+
+Logger used to print build status (`webpack building...`, `webpack built <hash> in <ms>`). Pass `false` to disable logging from the hot middleware.
+
+#### `hot.statsOptions`
+
+Type: `Boolean | Object`
+Default: `undefined`
+
+Webpack stats options used when serializing compilation results for the SSE payload. Forwarded to `stats.toJson(...)`.
+
 ## API
 
 `webpack-dev-middleware` also provides convenience methods that can be use to