we need a contributing.md for ISC DHCP
We had some stuff about how to contribute on the web site, I think that content is mostly now here: https://kb.isc.org/docs/contributing-to-iscs-open-source
it can be boilerplate. it should probably cover at least:
- how to submit a patch (presumably now via gitlab?)
- that your contribution will be covered by the current license for the project
- that you need to submit tests and doc for your contribution
- if there is still a contrib directory, what are the rules for what goes in there (e.g. ldap stuff?)