Add documentation (template?) for GitHub CI/CD workflow

[tschaffter]

Similar to #4 but for GitHub CI/CD workflow

A work in progress implementation is available in this PR: nlpsandbox/nlpsandbox-schemas#7

[tschaffter]

@jaeddy @jb-adams Here is a working example that I created for a repository that hosts multiple OpenAPI specifications:
https://github.com/Sage-Bionetworks/nlp-sandbox-schemas/blob/develop/.github/workflows/ci.yml

Additional information are available here:
nlpsandbox/nlpsandbox-schemas#30

[jb-adams]

Thanks @tschaffter !

Similar to #64 , I'd prefer to put this logic into the app itself to avoid replicating build/push logic across .travis.yml files for different GA4GH specs. I've started a feature branch to do this. In particular, the files gh-pages.js and git-config.js are handling similar logic as to what's in your ci.yml file.

I'm able to build, commit, and push to gh-pages all from a docker container running the app. Here is the repo containing a dummy "Hello World" API spec, that, when updated and pushed, triggers a push to gh-pages