Create a 'codecorgi is open source' page

[dvidsilva]

Explain why are we open sourcing, add links to github, code of conduct, procedures.

Something like this: https://about.gitlab.com/2016/07/20/gitlab-is-open-core-github-is-closed-source/

https://www.programmableweb.com/news/gitlab-changes-its-contributor-licensing-to-better-serve-open-source-projects/brief/2017/11/01