refactor: Use ESM (#8358)

* wip

* wip

* fix

* clean up

* Update tsconfig.json

* Update activitypub.ts

* wip

packages/backend/src/misc/content-disposition.ts

@@ -1,4 +1,4 @@
-const cd = require('content-disposition');
+import cd from 'content-disposition';
 
 export function contentDisposition(type: 'inline' | 'attachment', filename: string): string {
 	const fallback = filename.replace(/[^\w.-]/g, '_');