Add slot for tooltips/popovers rendering

[MAILPOET-2450]

assets/js/src/form_editor/components/editor.jsx

@@ -1,5 +1,6 @@
 import React from 'react';
 import { useSelect } from '@wordpress/data';
+import { Popover, SlotFillProvider } from '@wordpress/components';
 import classnames from 'classnames';
 import Header from './header.jsx';
 import Sidebar from './sidebar.jsx';
@@ -23,6 +24,7 @@ export default () => {
   });
   return (
     <div className={layoutClass}>
+      <SlotFillProvider>
         <Header />
         <div className="edit-post-layout__content">
           <Notices />
@@ -35,6 +37,8 @@ export default () => {
         <div>
           { sidebarOpened ? <Sidebar /> : null }
         </div>
+        <Popover.Slot />
+      </SlotFillProvider>
     </div>
   );
 };