Add a copy bugzero checklist button to GH issues

[tgolen]

This is part of https://github.com/Expensify/Expensify/issues/438990.

Tests

1. I manually added the comment to this test issue which contains the copy checklist button
2. Click the button
3. Verify that the checklist is posted from your account

[tgolen]

I updated the PR with what the final path should be, which means this doesn't need to be on HOLD. If you want to test it, you need to update the path to the checklist to be:

https://raw.githubusercontent.com/Expensify/App/f1e20914e4a9f3065457048e6a396fa0c841b0ad/contributingGuides/BUGZERO_CHECKLIST.md

[tgolen]

I'll go ahead and deploy this