[`coq/bot`] Track issues encountered since using this bot

[myii]

There have been a variety of problems encountered since using the bot. This issue is a catch-all for the issues that have been reported:

• https://github.com/coq/bot/issues/120
• https://github.com/coq/bot/issues/121
• https://github.com/coq/bot/issues/123
• https://github.com/coq/bot/issues/124
• https://github.com/coq/bot/issues/127