Create CODE_OF_CONDUCT.md
Create CODE_OF_CONDUCT.md

Ticket is referenced in [#Issue 1](https://github.com/pallets/meta/issues/1) in the Meta repo.
Spoke with @davidism and the decision was to use Contributor Covenant. It has easy GitHub integration and quality text.

For context, Here is a comparison of different codes of conduct from geek feminism:
Contributor Covenant looks like it is a good default because it covers:

Descriptions of common but unacceptable behavior
Reporting instructions with contact information
Information about enforcement
Clear demarcation between anti-harassment policy and general community guidelines
pallets/flask,fkazimierczak/flask,fkazimierczak/flask,drewja/flask,fkazimierczak/flask,pallets/flask,drewja/flask,mitsuhiko/flask,mitsuhiko/flask,pallets/flask,drewja/flask