Add Sentry to client for error handling (#43920)

Co-authored-by: Oliver Eyton-Williams <ojeytonwilliams@gmail.com>

client/src/utils/report-error.ts

@@ -1,7 +1,15 @@
-// TODO: integrate with Sentry?
+import * as Sentry from '@sentry/gatsby';
+import envData from '../../../config/env.json';
+
+const { sentryClientDSN } = envData;
+
 export function reportClientSideError(
   e: Error,
-  message = 'Unhandled error'
-): void {
-  return console.error(`Client: ${message}`, e);
+  message = sentryClientDSN === null
+    ? 'Unhandled error'
+    : 'Error sent to Sentry'
+): string | void {
+  return sentryClientDSN === null
+    ? console.error(`Client: ${message}`, e)
+    : Sentry.captureException(e);
 }