feat: Hide Outline branding on custom domain share links

closes #1629

app/utils/domains.js

@@ -1,7 +1,16 @@
 // @flow
-import { stripSubdomain } from "shared/utils/domains";
+import { parseDomain, stripSubdomain } from "shared/utils/domains";
 import env from "env";
 
 export function getCookieDomain(domain: string) {
   return env.SUBDOMAINS_ENABLED ? stripSubdomain(domain) : domain;
 }
+
+export function isCustomDomain() {
+  const parsed = parseDomain(window.location.origin);
+  const main = parseDomain(env.URL);
+
+  return (
+    parsed && main && (main.domain !== parsed.domain || main.tld !== parsed.tld)
+  );
+}