ci/cd: replace settings bot by github action

[Kamil Samigullin]

Motivation: settings is not transparent; debugging and observing it are difficult.

E.g., I did manual fixes for kamilsk/dotfiles/issues/388, removed and attached/detached old labels by new.

[Kamil Samigullin]

bad example and extra motivation #66 (comment)

[Kamil Samigullin]

research and try:

• https://github.com/marketplace/actions/github-action-to-run-probot-settings
• repository-settings/app#409
• https://github.com/probot/adapter-github-actions
• https://jasonet.co/posts/probot-app-or-github-action/
• https://github.com/repository-settings

[Kamil Samigullin]

related to octomation/settings-action/issues/16