Summary:
- Fix base href in HelpScout beacon when showing articles (in particular for Firefox)
- Show the 'Answers' tab normally except when reporting an error.
- Combine the "Give Feedback" and "Help Center" buttons into one that normally
opens the beacon (with a link to Help Center and to Community Forum), and a
smaller one that opens the Help Center site in a new tab.
- Update HELP_SCOUT_* env vars to use _V2 suffix, to allow them to coexist with
code using the previous beacon.
Test Plan: Updated the browser test to check the new behavior.
Reviewers: georgegevoian
Reviewed By: georgegevoian
Differential Revision: https://phab.getgrist.com/D3170