Add setup using Bot Accounts (App)

[Andre601]

I recently discovered that you can create and use a GitHub App (Bot account) for Actions by using the github-app-token action by tibdex.

This is useful as a user/org can have a dedicated app, rather than a PAT for actions that require one such as marking a PR as ready.

Perhaps the readme should mention a possible setup using a dedicated app for people who don't want to use a dedicated account (or their own) for a PAT.

[Andre601]

By the looks of it are you already aware of this solution...

You seem to use your own version, which is a fork of the above mentioned one... I now wonder if there are significant differences to the original