Prevent iframe embedding for dotcom (except on tldraw.com) (#2947)

This PR fixes a check on whether the dot com multiplayer editor has been
loaded in an iframe.

It tries to keep it working on tldraw.com itself.

### Change Type

- [x] `patch` — Bug fix

### Test Plan

1. Load me in an iframe

scripts/lib/file.ts

@@ -45,7 +45,7 @@ export async function writeCodeFile(
 	const formattedCode = await prettier.format(
 		`
 		// This file is automatically generated by ${generator}.
-		// Do not edit manually.
+		// Do not edit manually. Or do, I'm a comment, not a cop.
 
 		${code}
 	`,