Readme: Add Alpine Linux package

[jirutka]

Note: Alpine 3.13 has not been released yet, it should be till the end of this year.

[casey]

Awesome, thank you very much for creating the package!

Should this be merged after 3.13 releases, so that Alpine users aren't confused that the package isn't available yet?

[jirutka]

Awesome, thank you very much for creating the package!

You’re welcome!

Should this be merged after 3.13 releases, so that Alpine users aren't confused that the package isn't available yet?

Yes, it will be better.

[casey]

Sounds good, I'll check around Jan 1st, which is when I think it's due out. But if I forget, please feel free to ping the PR.

[jirutka]

Alpine 3.13.0 is released! :)

[casey]

Merged, thank you so much!

[casey]

(I removed the version, just because we don't have it for other distros, and I think it might look nicer as its own column if we did add it. Also, I changed the apk link to the apk docs, since that's probably what's most useful for someone looking to install just on Alpine.)