Setup CI via GitHub action

[lutangar]

This essentially setup CI/CD as Github actions.

I took some inspirations from https://github.com/Level/leveldown/blob/master/.github/workflows/release.yml to automate the prebuilds.

The test.yml workflow test on a variety of platform and node version.
See for example:
https://github.com/larriereguichet/alphacep-ref-napi/actions/runs/1530682216

The release.yml workflow create the prebuilds artefact create a Github release and publish the package to npm.
See an example of release:
https://github.com/larriereguichet/alphacep-ref-napi/releases/tag/3.0.3

As for the next steps I would recommend to:

1. Create an alphacep organisation on npm (if not already):
   https://www.npmjs.com/org/create
2. Generate a publish npm access token:
   https://www.npmjs.com/settings/nshmyrev/tokens
3. Add it as NPM_TOKEN to the repository secrets:
   https://github.com/alphacep/ref-napi/settings/secrets/actions
4. Bump version number in package.json and push a new tag to publish the new release:

git tag -f 4.0.1
git push origin --tags

Hope it helps,
Cheers!