js: ignore errors generated by a Microsoft crawler

Sentry has a lot of Javacript errors stating:

> UnhandledRejection: Non-Error promise rejection captured with value: Object Not Found Matching Id:2 

This is apparently caused by a Microsoft crawler (maybe for scanning
targets of email links), and can be safely ignored.

See https://forum.sentry.io/t/unhandledrejection-non-error-promise-rejection-captured-with-value/14062/12

app/javascript/shared/track/sentry.js

@@ -4,7 +4,15 @@ const { key, enabled, user, environment, browser } = gon.sentry || {};
 
 // We need to check for key presence here as we do not have a dsn for browser yet
 if (enabled && key) {
-  Sentry.init({ dsn: key, environment });
+  Sentry.init({
+    dsn: key,
+    environment,
+    ignoreErrors: [
+      // Ignore errors generated by a Microsoft crawler.
+      // See https://forum.sentry.io/t/unhandledrejection-non-error-promise-rejection-captured-with-value/14062
+      'Non-error promise rejection captured with keys'
+    ]
+  });
 
   Sentry.configureScope((scope) => {
     scope.setUser(user);