Try adding a page heading

This is a work in progress, which adds a page heading for screen readers. @afercia can you take a look and see if this mitigates #503?

If yes, then we'd need to wrap the actual label into a function so it not only outputs the right post type, but indeed is translatable.

gutenberg.php

@@ -30,6 +30,7 @@ function the_gutenberg_project() {
 	?>
 	<div class="nvda-temp-fix screen-reader-text">&nbsp;</div>
 	<div class="gutenberg">
+		<h1 class="screen-reader-text">Edit Post</h1>
 		<div id="editor" class="gutenberg__editor"></div>
 	</div>
 	<?php