docs: document global entry behavior in EntryPlugin (#12105)

* Initial plan

* docs: document global entry behavior in EntryPlugin

Add documentation for global entry behavior (when name is undefined):
- Global entries are now injected into both regular and async entrypoints
- Includes use cases for webpack-dev-server and ModuleFederationPlugin
- Added examples showing how global entries work with Workers

Related to PR #12096

Co-authored-by: chenjiahan <7237365+chenjiahan@users.noreply.github.com>

* Update entry-plugin.mdx

* Update entry-plugin.mdx

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: chenjiahan <7237365+chenjiahan@users.noreply.github.com>
Co-authored-by: neverland <chenjiahan.jait@bytedance.com>

Author: Copilot

website/docs/en/plugins/webpack/entry-plugin.mdx

@@ -39,4 +39,21 @@ type EntryOptions =
 
 If `options` is a string, its value will be used as `name`.
 
-Please refer to [Entry Description Object](/config/entry#entry-description-object) for all available options.
+Refer to [Entry description object](/config/entry#entry-description-object) for all available options.
+
+## Global entry
+
+When the plugin's `name` option is set to `undefined`, the entry is treated as a global entry. It's automatically injected into:
+
+1. All regular entry chunks
+2. All asynchronous entries (for example, worker chunks created with `new Worker()`)
+
+This allows you to inject global runtime code, such as the dev server's HMR runtime or the initialization logic for module federation.
+
+```js
+new rspack.EntryPlugin(
+  context,
+  './global-runtime.js',
+  { name: undefined }
+);
+```

website/docs/zh/plugins/webpack/entry-plugin.mdx

@@ -40,3 +40,20 @@ type EntryOptions =
 当 `options` 为字符串时，它的值会被作为 `name` 使用。
 
 请参考 [入口描述对象](/config/entry#入口描述对象) 了解所有可用的选项。
+
+## 全局入口
+
+当插件的 `name` 选项为 `undefined` 时，该入口被视为全局入口，它会自动注入到：
+
+1. 所有常规入口 chunk
+2. 所有异步入口（例如通过 `new Worker()` 创建的 worker chunk）
+
+这可以用于注入一段全局代码，例如 dev server 的热更新运行时代码，或是模块联邦的初始化逻辑。
+
+```js
+new rspack.EntryPlugin(
+  context,
+  './global-runtime.js',
+  { name: undefined }
+);
+```