feat(plugin-legacy): support additionalLegacyPolyfills

close #1475

Author: yyx990803

packages/plugin-legacy/README.md

@@ -49,6 +49,14 @@ export default {
 
   Set to `false` to avoid generating polyfills and handle it yourself (will still generate legacy chunks with syntax transformations).
 
+### `additionalLegacyPolyfills`
+
+- **Type:** `string[]`
+
+  Add custom imports to the legacy polyfills chunk. Since the usage-based polyfill detection only covers ES language features, it may be necessary to manually specify additional DOM API polyfills using this option.
+
+  Note: if additional plyfills are needed for both the modern and legacy chunks, they can simply be imported in the application source code.
+
 ### `ignoreBrowserslistConfig`
 
 - **Type:** `boolean`

packages/plugin-legacy/index.d.ts

@@ -13,6 +13,7 @@ export interface Options {
    * default: true
    */
   polyfills?: boolean | string[]
+  additionalLegacyPolyfills?: string[]
   /**
    * default: false
    */

packages/plugin-legacy/index.js

@@ -56,6 +56,11 @@ function viteLegacyPlugin(options = {}) {
       }
     })
   }
+  if (Array.isArray(options.additionalLegacyPolyfills)) {
+    options.additionalLegacyPolyfills.forEach((i) => {
+      legacyPolyfills.add(i)
+    })
+  }
 
   /**
    * @type {import('vite').Plugin}