feat: Add CDN support (#1817)

* chore: CSP

* chore: Optionally use CDN for serving images

app/scenes/Document/components/DataLoader.js

@@ -24,8 +24,8 @@ import Loading from "./Loading";
 import SocketPresence from "./SocketPresence";
 import { type LocationWithState, type Theme } from "types";
 import { NotFoundError, OfflineError } from "utils/errors";
-import isInternalUrl from "utils/isInternalUrl";
 import { matchDocumentEdit, updateDocumentUrl } from "utils/routeHelpers";
+import { isInternalUrl } from "utils/urls";
 
 type Props = {|
   match: Match,