Add arm64 arch

[zerodivisi0n]

Since arm64 architecture is quite popular nowadays (new Apple laptops, Raspberry Pi), I thinks that it's a good idea to have builds for it.

[zerodivisi0n]

Unfortunately, this won't work for Docker images, which are built by a separate workflow.
GoReleaser supports Docker Images, so it is possible to switch building to it. I can do that, if you don't mind.

[lc]

Hey @zerodivisi0n,

This is a great idea! I do use arm64 personally, so not sure how I didn't think of having a build for it haha. I think not having it for Docker images is probably fine for now, unless you'd like to build that out.

[zerodivisi0n]

Thanks for quick response, @lc!
I think I can add fixes for Docker images in a few days.