The .mailmap file is used by git-shortlog when creating summaries of
commits for releases, etc. Contributors who use multiple email
addresses (e.g. jared@tlon.io, jared@jtobin.io) or who would like their
name formatted in a particular manner (e.g. 'Jared Tobin' instead of
'jtobin') can add entries to .mailmap to unify their commits under a
single heading.
To initialise the file, I've added enough entries to ensure there are no
duplicate authors when running 'git shortlog --since="1 year ago"'.
