docs(module): document module.parser.javascript.anonymousDefaultExportName (#8242)

Webpack 5.107 introduces a new JS parser option that controls whether
webpack sets .name to "default" on anonymous default-export functions
and classes (per the ES spec). The fix-up was added in 5.106 but the
extra Object.defineProperty calls inflate bundles, so the option
defaults to true for applications and false for libraries (when
output.library is set). Documents the option under
module.parser.javascript.

Refs: webpack/webpack#20894

Author: bjohansebas

src/content/configuration/module.mdx

@@ -710,6 +710,33 @@ export default {
 
 It's allowed to configure those options in [`Rule.parser`](/configuration/module/#ruleparser) as well to target specific modules.
 
+#### module.parser.javascript.anonymousDefaultExportName
+
+<Badge text="5.107.0+" />
+
+Controls whether webpack sets `.name` to `"default"` for anonymous default-export functions and classes, matching the ES spec for native ESM. When enabled, webpack injects a small runtime helper (`__webpack_require__.dn`) that calls `Object.defineProperty(...)` on the export to set the `.name` value.
+
+- Type: `boolean`
+- Default: `true` for applications, `false` for libraries (when [`output.library`](/configuration/output/#outputlibrary) is set).
+
+Applications stay spec-compliant by default. Libraries skip the helper to keep bundle size small, since library consumers rarely rely on `.name === "default"`.
+
+To override the default explicitly:
+
+**webpack.config.js**
+
+```js
+export default {
+  module: {
+    parser: {
+      javascript: {
+        anonymousDefaultExportName: false,
+      },
+    },
+  },
+};
+```
+
 #### module.parser.javascript.commonjsMagicComments
 
 Enable [magic comments](/api/module-methods/#magic-comments) support for CommonJS.