feat: Add CDN support (#1817)

* chore: CSP

* chore: Optionally use CDN for serving images

app/utils/urls.js

@@ -0,0 +1,30 @@
+// @flow
+import { parseDomain } from "../../shared/utils/domains";
+import env from "env";
+
+export function isInternalUrl(href: string) {
+  if (href[0] === "/") return true;
+
+  const outline = parseDomain(window.location.href);
+  const parsed = parseDomain(href);
+
+  if (
+    parsed &&
+    outline &&
+    parsed.subdomain === outline.subdomain &&
+    parsed.domain === outline.domain &&
+    parsed.tld === outline.tld
+  ) {
+    return true;
+  }
+
+  return false;
+}
+
+export function cdnPath(path: string): string {
+  return `${env.CDN_URL}${path}`;
+}
+
+export function imagePath(path: string): string {
+  return cdnPath(`/images/${path}`);
+}