feature: ci with multiple targets

[jankapunkt]

This implements #34 in a way that our CI always tests for multiple node versions. Also removed the old travis file.

[jankapunkt]

You can also take a look at https://github.com/node-oauth/node-oauth2-server/actions/runs/1336376151

[HappyZombies]

@jankapunkt you need to target development branch! Not master ;)

Also, per this conversation about the linter, we realized that ESLint actually runs a specific version of Node 12 #30 (comment)

When we add linting to the pipeline, this will be an issue no doubt. So maybe there's a way to target that specific node version? I guess it doesn't really matter, since it's just a dev dependency for ESLint.

[jankapunkt]

Hey @HappyZombies my bad, changed.

Regarding eslint it runs fine on all three node versions in the ci so I think this should not be a problem, right?

[HappyZombies]

@jankapunkt I think you are right, I believe the CI uses whatever latest LTS is for Node 12, which is supported for that specific Node version.

Thanks, I'll do one final check, then approve and merge.

[HappyZombies]

@jankapunkt quick question on the npm run test being removed.