Editor: Ensure that the block editor can be used on the page post type.

Additionally, add a notice for when you are editing the "latest posts" page.

Fixes #45537.

Props cameronjonesweb, swissspidy, hannahmalcolm, Fantasy1125, ArnaudBan, grantmkin, youknowriad, knutsp, SergeyBiryukov, audrasjb, whyisjake. 


git-svn-id: https://develop.svn.wordpress.org/trunk@51116 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-admin/edit-form-blocks.php

@@ -313,6 +313,10 @@ $script = sprintf(
 );
 wp_add_inline_script( 'wp-edit-post', $script );
 
+if ( (int) get_option( 'page_for_posts' ) === (int) $post->ID ) {
+	add_action( 'admin_enqueue_scripts', '_wp_block_editor_posts_page_notice' );
+}
+
 require_once ABSPATH . 'wp-admin/admin-header.php';
 ?>