Draft: Docs feedback: Add troubleshooting section and guidance on enabling Operations when setting up Sentry Error Tracking

I found this through the Bad request when integrating with an on-premise Sentry installation.

In short: I can reproduce the behavior you encountered when Operations is disabled for a project -- with a working Sentry token.

• Q: In the impacted project, would you please browse to Settings > General, expand Visibility, project features, permissions and check whether Operations is set to On or Off?

If it is set to Off, please slide it to On, press Save Changes and then try the Connect button in Settings > Monitor > Error Tracking once more. It looks like a few other folks encountered this problem.