Docs: Github Actions

[luebken]

What problem are you facing?

This template contains a couple of Github actions e.g. https://github.com/upbound/upjet-provider-template/blob/main/.github/workflows/ci.yml which are not self-explanatory. But they are triggered automatically when users fork this repo.

How could Upbound help solve your problem?

Some basic documentations on how to use and adapt the Github actions.

[luebken]

Also it fails (at least initially)

3s
Run make publish BRANCH_NAME=${GITHUB_REF##*/}
  make publish BRANCH_NAME=${GITHUB_REF##*/}
  shell: /usr/bin/bash -e {0}
  env:
    GO_VERSION: [1](https://github.com/luebken/provider-vultr/actions/runs/3427882834/jobs/5711428559#step:14:1).19
    GOLANGCI_VERSION: v1.50.0
    DOCKER_BUILDX_VERSION: v0.8.[2](https://github.com/luebken/provider-vultr/actions/runs/3427882834/jobs/5711428559#step:14:2)
    UPBOUND_MARKETPLACE_PUSH_ROBOT_USR: 
    GOROOT: /opt/hostedtoolcache/go/1.19.2/x64
11:54:[3](https://github.com/luebken/provider-vultr/actions/runs/3427882834/jobs/5711428559#step:14:3)9 [ .. ] Skipping image publish for xpkg.upbound.io/upbound/upjet-provider-template:v0.0.0-1.ga569[4](https://github.com/luebken/provider-vultr/actions/runs/3427882834/jobs/5711428559#step:14:4)a3
Publish is deferred to xpkg machinery
11:[5](https://github.com/luebken/provider-vultr/actions/runs/3427882834/jobs/5711428559#step:14:5)4:40 [ OK ] Image publish skipped for xpkg.upbound.io/upbound/upjet-provider-template:v0.0.0-1.ga5[6](https://github.com/luebken/provider-vultr/actions/runs/3427882834/jobs/5711428559#step:14:6)94a3
11:54:40 [ .. ] Pushing package xpkg.upbound.io/upbound/upjet-provider-template:v0.0.0-1.ga5694a3
up: error: GET https://xpkg.upbound.io/service/token?scope=repository%3Aupbound%2Fupjet-provider-template%3Apush%2Cpull&service=xpkg.upbound.io: unexpected status code 404 Not Found
11:54:42 [FAIL]
make[1]: *** [build/makelib/xpkg.mk:9[7](https://github.com/luebken/provider-vultr/actions/runs/3427882834/jobs/5711428559#step:14:7): xpkg.release.publish.xpkg.upbound.io/upbound.upjet-provider-template] Error 1
make: *** [build/makelib/common.mk:4[11](https://github.com/luebken/provider-vultr/actions/runs/3427882834/jobs/5711428559#step:14:12): publish] Error 2
Error: Process completed with exit code 2.

[luebken]

one example of a confused user https://crossplane.slack.com/archives/C01718T2476/p1670287493600079