* Add Contributor Covenant v1.4

v2.0 is the latest version, and we can always upgrade to that later if
desired. As of 2020/07/23, v1.4 has been adopted and/or adapted by
Golang, React, and many other prominent OSS projects.

* Add basic CONTRIBUTING doc

* Add basic SECURITY doc

* Add README

* Update Ruby + Python package manifests

* Add Apache-2.0 license