Automatic builds using Github Actions

[Voker57]

This will build a mod archive from every commit to specified branch(es), and make a pre-release with file attached to it. You can see how it works here https://github.com/Voker57/wtp/releases/tag/development

Potential improvements:

• A release is a >1GB file with most data unchanged. Nightingale suggested using some kind of incremental releases, this can be implemented if there's an agreement on how it should be done
• Fastdep is not used because it doesn't work for some reason. It could theoretically speed up builds.

[Voker57]

I have replaced the script hacks with use of environment variables to avoid asking for input. Incremental releases, after consideration, would require a rather complicated setup with questionable value, so this will be excluded from this PR. The request is ready to merge.

[Nightinggale]

I'm not sure using compile.pl is the right move for this, but given that it reverts back to normal without specific environmental variables, I suppose it's doable. I will take a closer look at this when I get time to do so.