docs: fix the hot option reference and add a webpack-hot-middleware migration guide

The changeset advertised a `log` option that fails validation (it is
`progress`), `hot.statsOptions` documented the boolean form the schema
no longer accepts, `hot.path` now notes the required leading slash, and
the launch-editor sentence that had landed inside the `paginate`
parenthetical is back with `openEditorEndpoint`, where it belongs.

Also adds a "Migrating from webpack-hot-middleware" section: server and
webpack-config before/after, an option mapping table, and the
programmatic API equivalents.

Author: bjohansebas

.changeset/hot-middleware-migration.md

@@ -2,4 +2,4 @@
 "webpack-dev-middleware": minor
 ---
 
-Added a `hot` option that enables hot module replacement, replacing the need for `webpack-hot-middleware`. Pass `hot: true` to enable with defaults, or `hot: { path, heartbeat, log, statsOptions }` to customize. The client runtime is served by the middleware itself.
+Added a `hot` option that enables hot module replacement, replacing the need for `webpack-hot-middleware`. Pass `hot: true` to enable with defaults, or `hot: { path, heartbeat, progress, statsOptions }` to customize. The client runtime is served by the middleware itself.