Mistify needs a Code of Conduct

[nshalman]

Issue Description

We need a Code of Conduct in place before the hordes of community contributors show up.
I'll be investigating a few options with notes in this issue and will follow up with a pull request of my recommendation.

[nshalman]

http://contributor-covenant.org/ is one option that I like.

[nshalman]

At a bare minimum we need an email address to handle abuse reports.
Can we use the mistify.io domain for that? At worst we could put my email address in as a placeholder.

I was doing further research, but I think that Contributor Covenant provides us with a solid enough foundation that we can defer that for later.

Once we figure out what to do about the email address I'll open pull requests for the monorepo and the website.