FR: Add bot to mark issues as stale

## Problem to solve:
We have lots of Github issues across our package repositories that have gone stale. It would be a big LOE to manually go through all of them and mark them as stale ourselves. Also, it feels a little mean to mark them as stale from our own accounts lol

## Expected solution:
When the last comment is from a member of our team and X number of days have passed, a github bot will say something like
"This issue has been marked as stale and deprioritized by the Fivetran Solution Analytics' team. Add a new comment in the thread to get this issue unmarked as stale and reprioritized."

I prefer marking the issue as stale rather than closing it out in case other customers want to pick it back up, but that's an alternative solution that i believe dbt-labs uses.

The issue names no files, tests, or entry points. Start by inspecting the repository's automation setup and how GitHub issue comments and state are handled; done means a bot can identify issues whose last comment is from a team member, mark them stale after a configured number of days, and restore them when a new comment is added.

Written by the indexing model from the issue text.