Add native block-editor support

• Add wp-scripts for build
• Enqueue script, excluding it from widget block editor
• Localize script with configurable/filterable options
• Localize script with titles for post types to match current functionality
• Register meta and set sanitization callbacks
• Allow meta to be accessed via endpoint
• Create sidebar plugin to show the two fields used by the plugin

inc/class-external-permalinks-redux-block-editor.php

@@ -8,4 +8,15 @@
 /**
  * Class Block_Editor.
  */
-class External_Permalinks_Redux_Block_Editor {}
+class External_Permalinks_Redux_Block_Editor {
+	use External_Permalinks_Redux_Singleton;
+
+	/**
+	 * Set up class.
+	 *
+	 * @return void
+	 */
+	protected function _setup() {
+		// TODO: Implement _setup() method.
+	}
+}