Unit tests and coding standards

Updates JS to accommodate both Gutenberg and the Classic editor. Also introduces unit tests and conforms to coding standards.

Fixes #2 (closed) Fixes #3 (closed)

tests/test-hooks.php

@@ -72,10 +72,10 @@ class TestHooks extends WP_UnitTestCase {
 
 		for ( $i = 0; $i < $iterations; $i++ ) {
 			wp_update_post(
-				[
+				array(
 					'ID'           => $post_id,
 					'post_content' => wp_rand(),
-				]
+				)
 			);
 		}