service-worker check:

- on-load, display error if service worker support is not available
- for embeds, display service worker unavailable error right away, don't attempt to load iframe
trailing slash check: redirect http://example.com -> http://example.com/
resources/page query: if no query= param is set, use url as query (when switching from replay, url is used as query)

src/pageutils.js

@@ -9,6 +9,11 @@ async function registerSW(name = "sw.js", scope = "./") {
     resolve = res;
     reject = rej;
   });
+
+  if (!navigator.serviceWorker) {
+    console.error("Service Workers not supported");
+    reject();
+  }
   
   register(scope + name, {
     registrationOptions: { scope },