* Update to capture server exceptions and more

- Adds test cases for several server and client-side exceptions
- Allows capturing more server-side exceptions by overriding _error.js and using Sentry.captureException() within
- Use @sentry/node on the server
- Rely on Next.js's React Error Boundary instead of creating our own in _app.js

* Update test notes

Found some differences while testing in production

* Remove accidental mount throw on test 8

* Add note about server-side source maps

* Linting fixes