Block Editor: Display notice to the user when JavaScript is disabled.

Currently, when viewing the block editor with JavaScript disabled, the user sees a blank admin page with the admin menu sidebar. This adds an admin notice informing the user that JavaScript is required for the new block editor.

Props mkaz, pento, azaozz, ocean90, desrosj.
Fixes #45453.
Built from https://develop.svn.wordpress.org/trunk@44437


git-svn-id: http://core.svn.wordpress.org/trunk@44268 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-admin/css/common-rtl.css

@@ -560,6 +560,10 @@ code {
 	margin: 10px 2px 0 20px;
 }
 
+.wrap.block-editor-no-js {
+	padding-right: 20px;
+}
+
 .wrap > h2:first-child, /* Back-compat for pre-4.4 */
 .wrap [class$="icon32"] + h2, /* Back-compat for pre-4.4 */
 .postbox .inside h2, /* Back-compat for pre-4.4 */

wp-admin/css/common.css

@@ -560,6 +560,10 @@ code {
 	margin: 10px 20px 0 2px;
 }
 
+.wrap.block-editor-no-js {
+	padding-left: 20px;
+}
+
 .wrap > h2:first-child, /* Back-compat for pre-4.4 */
 .wrap [class$="icon32"] + h2, /* Back-compat for pre-4.4 */
 .postbox .inside h2, /* Back-compat for pre-4.4 */