Create CODE_OF_CONDUCT.md

[hanbollar]

adding a default base - using mozilla as copy since that's a common base - we can make this more detailed later on

[render[bot]]

Your Render PR Server URL is https://examples-mrjs-pr-624.onrender.com.

Follow its progress at https://dashboard.render.com/static/srv-coulrt4f7o1s73bdjg2g.