github-policy bot should look for issues with "needs: upvote" that cross specific thresholds and set a special label accordingly

Right now, we don't have visibility over issues that are getting a lot of upvotes other than to check-in manually on an ad-hoc basis. Would like the bot to make this visible to us. For example, we could have a rule that says "if an issue goes from 4->5 upvotes, add back needs: triage"

The issue names the github-policy bot and the needs: upvote label; start by locating the bot's configuration and existing issue-labeling rules. Define the upvote thresholds and the special label behavior, including the example transition from 4 to 5 upvotes, then verify that qualifying issues receive the intended label.

Written by the indexing model from the issue text.