🚀 Feature: Allow filtering on labels

[JoshuaKGoldberg]

Bug Report Checklist

• I have pulled the latest main branch of the repository.
• I have searched for related issues and found none that matched my issue.

Overview

Right now, prune-github-notifications allows filtering on reason and title. But sometimes an individual will send a PR that just so happens to look like a bot's PR. It'd be nice to be able to filter to just the PRs that match a configurable list of labels. A couple of example use cases:

• labels: [/^dependencies$/]: would work for many straightforward repos
• labels: [/^bot$/, /dependencies/]: would work for some more complex repos that use multiple bot-indicator labels

Let's add in a --label CLI option & label Node.js option!

Additional Info

No response