add a tpa person to listmaster

Right now listmaster@lists.tpo is me, qbi, and atagar. This is the default owner of many of the mailing lists.

When lists like tor-announce@ or tor-dev@ get a mail, it causes a flood of bounce responses to go back to listmaster, e.g. from yahoo (#34134).

anarcat suggested at one point that we should put one of the active new TPA people on this list, so they can get a better intuition for the scope of the problem and how it changes over time.

Is @lavamind the right candidate?

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