docs(migration): add a note about using a CommonJS file as an entrypoint (#18577)

Author: sapphi-red

docs/guide/migration.md

@@ -88,7 +88,9 @@ There are other breaking changes which only affect few users.
 - [[#18209] refactor!: bump minimal terser version to 5.16.0](https://github.com/vitejs/vite/pull/18209)
   - Minimal supported terser version for [`build.minify: 'terser'`](/config/build-options#build-minify) was bumped to 5.16.0 from 5.4.0.
 - [[#18231] chore(deps): update dependency @rollup/plugin-commonjs to v28](https://github.com/vitejs/vite/pull/18231)
-  - [`commonjsOptions.strictRequires`](https://github.com/rollup/plugins/blob/master/packages/commonjs/README.md#strictrequires) is now `true` by default (was `'auto'` before). This may lead to larger bundle sizes but will result in more deterministic builds.
+  - [`commonjsOptions.strictRequires`](https://github.com/rollup/plugins/blob/master/packages/commonjs/README.md#strictrequires) is now `true` by default (was `'auto'` before).
+    - This may lead to larger bundle sizes but will result in more deterministic builds.
+    - If you are specifying a CommonJS file as an entry point, you may need additional steps. Read [the commonjs plugin documentation](https://github.com/rollup/plugins/blob/master/packages/commonjs/README.md#using-commonjs-files-as-entry-points) for more details.
 - [[#18243] chore(deps)!: migrate `fast-glob` to `tinyglobby`](https://github.com/vitejs/vite/pull/18243)
   - Range braces (`{01..03}` ⇒ `['01', '02', '03']`) and incremental braces (`{2..8..2}` ⇒ `['2', '4', '6', '8']`) are no longer supported in globs.
 - [[#18493] refactor!: remove fs.cachedChecks option](https://github.com/vitejs/vite/pull/18493)