Add FreeBSD runner image

[Thefrank]

This was requested two years ago: #2529 and closed due to time/resource constraints
[to my understanding of: maintenance concerns ]

Since then people have created workarounds:
actions/runner#385 (this topic predates the issue above)
https://github.com/ChristopherHX/github-act-runner
https://github.com/marketplace/actions/cross-platform-action
https://github.com/myb-project/guide/blob/main/en/gh_runners.md
https://github.com/davidchisnall/act-pot (used here microsoft/snmalloc#360)

These all come at a cost either in significant time to setup or resource cost in using nested VMs

(packer has a FreeBSD, NetBSD, OpenBSD, and even Solaris version: https://developer.hashicorp.com/packer/downloads)

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• I have searched for similar discussion topics: https://github.com/actions/runner-images/discussions?discussions_q=freebsd)
• I can not open this as an issue as those are restricted to a select number of predetermined templates (e,g., request new tool but no request platform)

[erik-bershel]

Hey @Thefrank!
We still don't have plans to provide more images mostly due to maintenance concerns.

[Thefrank]

Thanks for the quick reply!

I am willing to take the time to, either alone or with the assistance of a code owner here, to make a PR adding image generation for FreeBSD (changes would also like be needed here https://github.com/actions/runner too) . Would such a PR be accepted?

[mikhailkoliada]

@Thefrank Hello! We do not accept contributions for OSes other than Ubuntu/Windows/macOS

[Thefrank]

@mikhailkoliada thank you for information.
Can this be added somewhere so that people with other OSes don't make my same mistake? (e.g, https://github.com/actions/runner/blob/main/docs/contribute.md + https://github.com/actions/runner-images/blob/main/CONTRIBUTING.md)?

edit: actions/runner#385 should be closed if you get a chance