Github Action for release (binary and docker)

[fopina]

• Added release.yml workflow to run goreleaser and docker build/push only for tags
• Excluded tags from main.yml workflow (as tags should have been tested when pushed to the branch and avoids re-running workflows on the same commits)
• Removed docker build from goreleaser to separate step using buildkit -> allows for multi-arch builds -> GoReleaser has had this open 2 years Support multi-platform docker images goreleaser/goreleaser#530 and it's still about the previous way (building each image and bundling the docker manifest), buildkit does it all in one go
• scripts/release no longer required, but left in case you want to do some manual release
• added arm/v7 build (for raspberry pi)

➜  dkron git:(fopina-patch-ga) docker run --rm dkron/dkron version
Name: Dkron
Version: 3.0.2
Codename: merichuas
Agent Protocol: 5 (Understands back to: 2)
➜  dkron git:(fopina-patch-ga) ssh sfpi docker run --rm dkron/dkron version
standard_init_linux.go:211: exec user process caused "exec format error"
➜  dkron git:(fopina-patch-ga) docker run --rm fopina/dkron:v3.0.2-12 version
Name: Dkron
Version: 3.0.2-12
Codename: merichuas
Agent Protocol: 5 (Understands back to: 2)
➜  dkron git:(fopina-patch-ga) ssh sfpi docker run --rm fopina/dkron:v3.0.2-12 version
Name: Dkron
Version: 3.0.2-12
Codename: merichuas
Agent Protocol: 5 (Understands back to: 2)

Left a few "fork friendly" items in workflow that won't affect dkron/dkron and make it easy to release patched versions from forks :D but we remove of course, if you prefer.

[fopina]

@Victorcoder and no <3 for this one too ^^ ?
Took quite a few builds to get it right 🔨

[fopinappb]

out of curiosity @Victorcoder , what leaves you uneasy on this PR? it's the simple change to GA that we discussed in gitter :)

[vcastellm]

Sorry for the delay @fopina didn't have time to look into it until now

[meshchaninov]

This works fine in rusberry pi 4 (ubuntu)

[vcastellm]

Aside from the comment it LGTM, thanks!

[vcastellm]

This is missing the Major version tag

[vcastellm]

I'm merging this, I will add the tag

[fopina]

Sorry, away from computer these days. Cool!