Fix links from old to new handbook (#15705)

Updates links to go straight to the section of the new handbook
location. A generic redirect is setup, but also better to refer directly
to the canonical URL.

README.md

@@ -40,7 +40,7 @@ Blocks are the unifying evolution of what is now covered, in different ways, by
 
 Imagine a custom `employee` block that a client can drag onto an `About` page to automatically display a picture, name, and bio of all the employees. Imagine a whole universe of plugins just as flexible, all extending WordPress in the same way. Imagine simplified menus and widgets. Users who can instantly understand and use WordPress—and 90% of plugins. This will allow you to easily compose beautiful posts like <a href="http://moc.co/sandbox/example-post/">this example</a>.
 
-Check out the <a href="https://wordpress.org/gutenberg/handbook/designers-developers/faq/">FAQ</a> for answers to the most common questions about the project.
+Check out the <a href="https://developer.wordpress.org/block-editor/contributors/faq/">FAQ</a> for answers to the most common questions about the project.
 
 ## Compatibility
 
@@ -71,7 +71,7 @@ Please see <a href="https://github.com/WordPress/gutenberg/blob/master/CONTRIBUT
 
 - <a href="http://matiasventura.com/post/gutenberg-or-the-ship-of-theseus/">Gutenberg, or the Ship of Theseus</a>, with examples of what Gutenberg might do in the future
 - <a href="https://make.wordpress.org/core/2017/01/17/editor-technical-overview/">Editor Technical Overview</a>
-- <a href="https://wordpress.org/gutenberg/handbook/contributors/design/">Design Principles and block design best practices</a>
+- <a href="https://developer.wordpress.org/block-editor/contributors/design/">Design Principles and block design best practices</a>
 - <a href="https://github.com/Automattic/wp-post-grammar">WP Post Grammar Parser</a>
 - <a href="https://make.wordpress.org/core/tag/gutenberg/">Development updates on make.wordpress.org</a>
 - <a href="https://wordpress.org/gutenberg/handbook/">Documentation: Creating Blocks, Reference, and Guidelines</a>

docs/designers-developers/developers/backward-compatibility/deprecations.md

@@ -59,7 +59,7 @@ For features included in the Gutenberg plugin, the deprecation policy is intende
 - The PHP function `gutenberg_get_block_categories` has been removed. Use [`get_block_categories`](https://developer.wordpress.org/reference/functions/get_block_categories/) instead.
 - The PHP function `register_tinymce_scripts` has been removed. Use [`wp_register_tinymce_scripts`](https://developer.wordpress.org/reference/functions/wp_register_tinymce_scripts/) instead.
 - The PHP function `gutenberg_register_post_types` has been removed.
-- The `gutenberg` theme support option has been removed. Use [`align-wide`](https://wordpress.org/gutenberg/handbook/designers-developers/developers/themes/theme-support/#wide-alignment) instead.
+- The `gutenberg` theme support option has been removed. Use [`align-wide`](https://developer.wordpress.org/block-editor/developers/themes/theme-support/#wide-alignment) instead.
 - The PHP function `gutenberg_prepare_blocks_for_js` has been removed. Use [`get_block_editor_server_block_settings`](https://developer.wordpress.org/reference/functions/get_block_editor_server_block_settings/) instead.
 - The PHP function `gutenberg_load_list_reusable_blocks` has been removed.
 - The PHP function `_gutenberg_utf8_split` has been removed. Use `_mb_substr` instead.

docs/designers-developers/developers/tutorials/block-tutorial/generate-blocks-with-wp-cli.md

@@ -62,7 +62,7 @@ This will generate 4 files inside the `movies` plugin directory. All files conta
  * Registers all block assets so that they can be enqueued through Gutenberg in
  * the corresponding context.
  *
- * @see https://wordpress.org/gutenberg/handbook/designers-developers/developers/tutorials/block-tutorial/writing-your-first-block-type/
+ * @see https://developer.wordpress.org/block-editor/tutorials/block-tutorial/writing-your-first-block-type/
  */
 function movie_block_init() {
 	$dir = dirname( __FILE__ );
@@ -109,23 +109,23 @@ add_action( 'init', 'movie_block_init' );
 ( function( wp ) {
 	/**
 	 * Registers a new block provided a unique name and an object defining its behavior.
-	 * @see https://wordpress.org/gutenberg/handbook/designers-developers/developers/block-api/#registering-a-block
+	 * @see https://developer.wordpress.org/block-editor/developers/block-api/block-registration/
 	 */
 	var registerBlockType = wp.blocks.registerBlockType;
 	/**
 	 * Returns a new element of given type. Element is an abstraction layer atop React.
-	 * @see https://wordpress.org/gutenberg/handbook/designers-developers/developers/packages/packages-element/
+	 * @see https://developer.wordpress.org/block-editor/packages/packages-element/
 	 */
 	var el = wp.element.createElement;
 	/**
 	 * Retrieves the translation of text.
-	 * @see https://wordpress.org/gutenberg/handbook/designers-developers/developers/packages/packages-i18n/
+	 * @see https://developer.wordpress.org/block-editor/packages/packages-i18n/
 	 */
 	var __ = wp.i18n.__;
 
 	/**
 	 * Every block starts by registering a new block type definition.
-	 * @see https://wordpress.org/gutenberg/handbook/designers-developers/developers/block-api/#registering-a-block
+	 * @see https://developer.wordpress.org/block-editor/developers/block-api/block-registration/
 	 */
 	registerBlockType( 'movies/movie', {
 		/**
@@ -151,7 +151,7 @@ add_action( 'init', 'movie_block_init' );
 		/**
 		 * The edit function describes the structure of your block in the context of the editor.
 		 * This represents what the editor will render when the block is used.
-		 * @see https://wordpress.org/gutenberg/handbook/designers-developers/developers/block-api/block-edit-save/#edit
+		 * @see https://developer.wordpress.org/block-editor/developers/block-api/block-edit-save/
 		 *
 		 * @param {Object} [props] Properties passed from the editor.
 		 * @return {Element}       Element to render.
@@ -167,7 +167,7 @@ add_action( 'init', 'movie_block_init' );
 		/**
 		 * The save function defines the way in which the different attributes should be combined
 		 * into the final markup, which is then serialized by Gutenberg into `post_content`.
-		 * @see https://wordpress.org/gutenberg/handbook/designers-developers/developers/block-api/block-edit-save/#save
+		 * @see https://developer.wordpress.org/block-editor/developers/block-api/block-edit-save/#save
 		 *
 		 * @return {Element}       Element to render.
 		 */