docs: describe how to configure CommonJS modules

In version 10, we have a new option for the `angular.json` file,
`allowedCommonJsDependencies`, so users can opt in to support
CommonJS modules.

aio/content/guide/build.md

@@ -262,6 +262,31 @@ Each budget entry is a JSON object with the following properties:
 
  </table>
 
+{@a commonjs-dependencies }
+## Allowing CommonJS dependencies
+
+<div class="alert is-important">
+It is recommended that you avoid depending on CommonJS modules in your Angular applications.
+Depending on CommonJS modules can prevent bundlers and minifiers from optimizing your application, which results in larger bundle sizes.
+Instead, it is recommended that you use <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/import">ECMAScript modules</a> in your entire application.
+For more information, see <a href="https://web.dev/commonjs-larger-bundles/">How CommonJS is making your bundles larger</a>.
+</div>
+
+The Angular CLI outputs warnings if it detects that your browser application depends on CommonJS modules.
+To disable these warnings, you can add the CommonJS module name to `allowedCommonJsDependencies` option in the `build` options located in `angular.json` file.
+
+<code-example lang="json">
+"build": {
+  "builder": "@angular-devkit/build-angular:browser",
+  "options": {
+     "allowedCommonJsDependencies": [
+        "lodash"
+     ]
+     ...
+   }
+   ...
+},
+</code-example>
 
 {@a browser-compat}