Becoming a committer: form for tracking readiness

Existing committers regularly discuss who to add as a committer. PostgreSQL
is a big and busy place, and many projects are well known to no more than a
few committers. To inform those discussions, we're experimenting with a
fillable form to capture a person's most relevant work. This helps each
committer in those discussions understand a person's contributions beyond the
projects the committer monitored. Committers familiar with the work will
complete the form for other committers to read.

We're sharing the form here for a few reasons:

- If you aim to become a committer, we encourage you to fill out the form
yourself and self-reflect or discuss it with your mentor to plan your path
forward.

- Even if you're not yet ready for commit access, developing in the direction
of the criteria will help PostgreSQL scale.

- We aim to be transparent about how we compare a person's work to some of the
longstanding criteria (https://www.postgresql.org/developer/committers/).

If you have questions about the form, feel free to ask on this thread. This
is an experiment, and we'll revise things over time.

(on behalf of the committers)