Script Modules API: Add import map polyfill for older browsers

Syncs the changes from https://github.com/WordPress/gutenberg/pull/58263. Adds a polyfill to make import maps compatible with unsported browsers (https://caniuse.com/import-maps).

Fixes #60348.
Props cbravobernal, jorbin, luisherranz, jonsurrell.



git-svn-id: https://develop.svn.wordpress.org/trunk@57492 602fd350-edb4-49c9-b593-d223f7449a82

tools/webpack/packages.js

@@ -93,6 +93,7 @@ module.exports = function (
 		'wp-polyfill-object-fit.js':
 			'objectFitPolyfill/src/objectFitPolyfill.js',
 		'wp-polyfill-inert.js': 'wicg-inert/dist/inert.js',
+		'wp-polyfill-importmap.js': 'es-module-shims/dist/es-module-shims.wasm.js',
 		'moment.js': 'moment/moment.js',
 		'react.js': 'react/umd/react.development.js',
 		'react-dom.js': 'react-dom/umd/react-dom.development.js',
@@ -121,6 +122,7 @@ module.exports = function (
 			'polyfill-library/polyfills/__dist/Node.prototype.contains/raw.js',
 		'wp-polyfill-dom-rect.min.js':
 			'polyfill-library/polyfills/__dist/DOMRect/raw.js',
+		'wp-polyfill-importmap.min.js': 'es-module-shims/dist/es-module-shims.wasm.js',
 	};
 
 	const phpFiles = {