Use goreleaser to generate binary builds

[juanfont]

For the time being only on new tags...

[cure]

I think we're missing a .goreleaser.yml file in the repo. I propose one with these contents:

builds:
  - main: cmd/headscale/headscale.go
    mod_timestamp: '{{ .CommitTimestamp }}'
    goarch:
      - amd64
      - arm64
    goos:
      - linux

Only the line that sets main is strictly necessary. The mod_timestamp line is nice so that we make reproducible builds. The goarch and goos values are there to limit the number of targets we build for.

I tested this in a dummy repo by playing around with goreleaser --snapshot --skip-publish --rm-dist and after setting a local tag, goreleaser --skip-publish --rm-dist.

[juanfont]

Brilliant move on my side, I left the most important file behind :(

[cure]

LGTM!