Change handbook links to the new wp.org URL (#3848)

README.md

@@ -66,7 +66,7 @@ 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="http://gutenberg-devdoc.surge.sh/reference/design-principles/">Design Principles and block design best practices</a>
+- <a href="https://wordpress.org/gutenberg/handbook/reference/design-principles/">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="http://gutenberg-devdoc.surge.sh/">Documentation: Creating Blocks, Reference, and Guidelines</a>
+- <a href="https://wordpress.org/gutenberg/handbook/">Documentation: Creating Blocks, Reference, and Guidelines</a>