Also release `private_comments` as a 64-bit linux binary

[filmil]

Would be useful to avoid having to build from source for 64-bit machines.

Thanks!

[masukomi]

Happy to accept a PR with this. I just don't have a linux machine to write and test such a thing on.

[filmil]

OK.

It seems that github actions could be used to build for linux.

[filmil]

I have a PR that handles this, and builds the binary automatically for 64-bit linux when a new release is tagged.
See here how it looks:
https://github.com/filmil/private_comments/releases/tag/v2.0.1

Needs to wait until #26 is merged.