Filter out browser extensions from error logging

Been getting a lot of errors I *think* from folks trying to add OWLS Pricer to Impress 2020 even though it doesn't work here! Reasonable to have happen though! I thought Sentry knew to ignore those, but I guess it doesn't?

In this change, we add some filtering to ignore errors triggered by extensions. This should keep them out of our inbox!

I wasn't able to test this very robustly locally. I'm mostly just crossing fingers!

src/app/App.js

@@ -98,6 +98,16 @@ Sentry.init({
       startTransactionOnLocationChange: false,
     }),
   ],
+  denyUrls: [
+    // Don't log errors that were probably triggered by extensions and not by
+    // our own app. (Apparently Sentry's setting to ignore browser extension
+    // errors doesn't do this anywhere near as consistently as I'd expect?)
+    //
+    // Adapted from https://gist.github.com/impressiver/5092952, as linked in
+    // https://docs.sentry.io/platforms/javascript/configuration/filtering/.
+    /^chrome-extension:\/\//,
+    /^moz-extension:\/\//,
+  ],
 
   // Since we're only tracking first-page loads and not navigations, 100%
   // sampling isn't actually so much! Tune down if it becomes a problem, tho.