Canvis a "Contributor reference letter policy"

Problem statement

We are often requested to give references for people in our community, however increasingly we're being asked by people who are not very active, or are very new to the community. This policy makes it clear what kind of reference we'll provide and the minimum expected term of contribution we expect to see.

Detailed proposal

Please see the PR build preview here: https://mautic-community-handbook--434.org.readthedocs.build/en/434/policies/contributor_reference.html

Benefits / impact

This benefits contributors as we're now being clear what their expectations should be if they wish to request a reference, and it benefits us because there's clarity, transparency and fairness as to who is and isn't entitled to receive a reference.

Potential challenges

I don't foresee any.

Resources needed

None

Suggested timeline

Recommend immediate implementation.

Additional information

PR here: https://github.com/mautic/mautic-community-handbook/pull/434/changes