ci: Add Github Actions workflows

[legobeat]

Migrating from Travis to GHA.
Travis will be removed in a follow-up.

[legobeat]

The reason npm i is timing out here is the same reason it's failing when running locally:

$ npm i
npm ERR! Error while executing:
npm ERR! /usr/bin/git ls-remote -h -t git://github.com/frozeman/WebSocket-Node.git
npm ERR!
npm ERR! fatal: unable to connect to github.com:
npm ERR! github.com[0: 20.27.177.113]: errno=Connection refused
npm ERR!
npm ERR!
npm ERR! exited with error code: 128

git protocol has been deprecated on GitHub for some time now.

This will be addressed separately in #2.