Block Editor: Add the initial set of block patterns.

Included patterns:

text-two-columns
two-buttons
two-images
text-two-columns-with-images
text-three-columns-buttons
large-header
large-header-paragraph
three-buttons
quote
testimonials

Props mcsf, nrqsnchz.
See #50550.

Built from https://develop.svn.wordpress.org/trunk@48334


git-svn-id: http://core.svn.wordpress.org/trunk@48103 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/class-wp-block-patterns-registry.php

@@ -38,7 +38,7 @@ final class WP_Block_Patterns_Registry {
 	 */
 	public function register( $pattern_name, $pattern_properties ) {
 		if ( ! isset( $pattern_name ) || ! is_string( $pattern_name ) ) {
-			_doing_it_wrong( __METHOD__, s__( 'Pattern name must be a string.' ), '5.5.0' );
+			_doing_it_wrong( __METHOD__, __( 'Pattern name must be a string.' ), '5.5.0' );
 			return false;
 		}