[Feature] Add Travis CI integration for commit linting

[csshugs]

As we now have commit linting in place, we should validate this remotely on GitHub as well.

[fuhlig]

Those packages might be worth a look:

• commitlint-config-squash-pr
• @commitlint/travis-cli.

https://www.conventionalcommits.org/en/v1.0.0-beta.2/#do-all-my-contributors-need-to-use-the-conventional-commit-specification

[csshugs]

#12 is merged.