Refactor: Revise pattern matching in uploaded file path detector. (#634)

This patch introduces a small change, where previously the detection for
user-uploaded content paths ran multiple checks against the path for possible
directories. Now, a single `RegExp` pattern checks in a single pass if the path
refers to one of the intended directories. Performance impact should be
negligible, but why do five times what can mostly be done once.

cc: @ironprogrammer whose work in #633 prompted this change.

packages/playground/remote/src/lib/is-uploaded-file-path.ts

@@ -1,9 +1,3 @@
 export const isUploadedFilePath = (path: string) => {
-	return (
-		path.startsWith('/wp-content/uploads/') ||
-		path.startsWith('/wp-content/plugins/') ||
-		path.startsWith('/wp-content/mu-plugins/') ||
-		path.startsWith('/wp-content/themes/') ||
-		path.startsWith('/wp-content/fonts/')
-	);
+	return /^wp-content\/(?:fonts|(?:mu-)?plugins|themes|uploads)\//.test(path);
 };