add filter to allow extending the list of post content blocks

docs/reference-guides/filters/block-filters.md

@@ -283,6 +283,24 @@ wp.hooks.addFilter(
 ```
 
 
+### `editor.postContentBlockTypes`
+
+Used to modify the list of blocks that should be enabled even when used inside a locked template. Any block that saves data to a post should be added here. Examples of this are the post featured image block. Which often gets used in templates but should still allow selecting the image even when the template is locked.
+
+_Example:_
+
+```js
+const addExampleBlockToPostContentBlockTypes = ( blockTypes ) => {
+	return [ ...blockTypes, 'namespace/example' ];
+};
+
+wp.hooks.addFilter(
+	'editor.postContentBlockTypes',
+	'my-plugin/post-content-block-types',
+	addExampleBlockToPostContentBlockTypes
+);
+```
+
 ## Removing Blocks
 
 ### Using a deny list

packages/editor/src/components/provider/disable-non-page-content-blocks.js

@@ -4,12 +4,13 @@
 import { useSelect, useDispatch } from '@wordpress/data';
 import { store as blockEditorStore } from '@wordpress/block-editor';
 import { useEffect } from '@wordpress/element';
+import { applyFilters } from '@wordpress/hooks';
 
-const PAGE_CONTENT_BLOCKS = [
+const PAGE_CONTENT_BLOCKS = applyFilters( 'editor.postContentBlockTypes', [
 	'core/post-title',
 	'core/post-featured-image',
 	'core/post-content',
-];
+] );
 
 function useDisableNonPageContentBlocks() {
 	const contentIds = useSelect( ( select ) => {