Skip (or ✅) GHA if only irrelevant files changed

[Al2Klimov]

Is your feature request related to a problem? Please describe.

GitHub actions take long even for files which don't really matter for build. Namely:

• ICINGA2_VERSION
• CHANGELOG.md
• doc/

Describe the solution you'd like

At least for Docker (takes most time) and/or Linux (many jobs) skip GitHub actions or mark them green (exit 0) if only files listed above changed.

Describe alternatives you've considered

• Auto-merge
• Keep force-merging such PRs if needed