Force focus on editor when toggling format

Since clicking the format button will cause focus to be moved out of
the editor. Ensuring focus will cause nodeChange to be triggered with
parent according to format applied.

See: 2ef33e2

blocks/components/editable/index.js

@@ -239,6 +239,8 @@ export default class Editable extends wp.element.Component {
 	}
 
 	toggleFormat( format ) {
+		this.editor.focus();
+
 		if ( this.isFormatActive( format ) ) {
 			this.editor.formatter.remove( format );
 		} else {