Please make membership of tskit-dev public

[jeromekelleher]

pinging @tskit-dev/all

Currently only 4 out of 17 members of tskit-dev have their membership made public. Seeing lots of people in the People page helps us to convince others that this is a welcoming and growing community, and may help to convince others that they'd like to join us. Therefore, please consider making your membership of the group 'public' (there's no pressure, of course; I'm guessing that most people don't realise that membership is private by default).