Docs: Add instructions for disabling the Block Directory

docs/designers-developers/developers/filters/editor-filters.md

@@ -50,3 +50,17 @@ It is set by default to the return value of the [`user_can_richedit`](https://de
 Default `true`. Indicates whether the user can access the code editor **in addition** to the visual editor.
 
 If set to false the user will not be able to switch between visual and code editor. The option in the settings menu will not be available and the keyboard shortcut for switching editor types will not fire.  
+
+### Block Directory
+
+The Block Directory enables installing new block plugins from [WordPress.org.](https://wordpress.org/plugins/browse/block/) It can be disabled by removing the actions that enqueue it. In WordPress core, the function is `wp_enqueue_editor_block_directory_assets`, and Gutenberg uses `gutenberg_enqueue_block_editor_assets_block_directory`. To remove the feature, use [`remove_action`,](https://developer.wordpress.org/reference/functions/remove_action/) like this:
+
+```php
+add_action(
+	'plugins_loaded',
+	function() {
+		remove_action( 'enqueue_block_editor_assets', 'wp_enqueue_editor_block_directory_assets' );
+		remove_action( 'enqueue_block_editor_assets', 'gutenberg_enqueue_block_editor_assets_block_directory' );
+	}
+);
+```