Fix CI

[jmank88]

Circle is broken - maybe a good time to switch to actions.

https://app.circleci.com/pipelines/github/gochain/rpc-proxy/1/workflows/1c0168cf-721d-4495-be54-356f024f9bc6/jobs/156

Otherwise, update this key:

git@github.com: Permission denied (publickey).
fatal: Could not read from remote repository.

[treeder]

Let's just switch to actions while we're here.

[jmank88]

Added actions for Go build/test and the default docker push to github packages: docker.pkg.github.com/gochain/rpc-proxy/rpc-proxy
Should we try this out?

Still need to add version bumps either way.

[jmank88]

The image is published publicly (https://github.com/gochain/rpc-proxy/packages/774328), but those pull instructions fail on auth. Is there something we can do to make it available? I'm not able to access package settings.

[jmank88]

I was able to replace the circle 'user key' so that it can fetch from the repo, but I'm not able to replace the 'deploy key' so that it can push the version bump.