Block Editor: Add missing package to the default export array.

Follow up on https://core.trac.wordpress.org/ticket/49358#comment:12.
We should add "warning" to the array of packages with default export to avoid the need for developers to use wp.warning.default.

Props gziolo, aduth.
Fixes #49436.

git-svn-id: https://develop.svn.wordpress.org/trunk@47301 602fd350-edb4-49c9-b593-d223f7449a82

tools/webpack/packages.js

@@ -220,6 +220,7 @@ module.exports = function( env = { environment: 'production', watch: false, buil
 				'token-list',
 				'server-side-render',
 				'shortcode',
+				'warning',
 			].map( camelCaseDash ) ),
 			new CustomTemplatedPathPlugin( {
 				basename( path, data ) {