[MM-58463] Remove defer for main/entry JS scripts (#27272)

webapp/channels/webpack.config.js

@@ -159,6 +159,7 @@ var config = {
             filename: 'root.html',
             inject: 'head',
             template: 'src/root.html',
+            scriptLoading: 'blocking',
             meta: {
                 csp: {
                     'http-equiv': 'Content-Security-Policy',