Add Camelid

Email from @camelid:

> HI there,
>
> I’m a new contributor and I just looked at Rust Thanks and noticed that my contributions are listed under two different capitalizations of my name: “Camelid" and “camelid". Could you make them both “Camelid"?
> 
> Thanks!
> 
> Camelid

Author: BatmanAoD

.mailmap

@@ -44,6 +44,7 @@ Brian Anderson <banderson@mozilla.com> <andersrb@gmail.com>
 Brian Anderson <banderson@mozilla.com> <banderson@mozilla.org>
 Brian Dawn <brian.t.dawn@gmail.com>
 Brian Leibig <brian@brianleibig.com> Brian Leibig <brian.leibig@gmail.com>
+Camelid <camelidcamel@gmail.com> <37223377+camelid@users.noreply.github.com>
 Carl-Anton Ingmarsson <mail@carlanton.se> <ca.ingmarsson@gmail.com>
 Carol (Nichols || Goulding) <carol.nichols@gmail.com> <193874+carols10cents@users.noreply.github.com>
 Carol (Nichols || Goulding) <carol.nichols@gmail.com> <carol.nichols@gmail.com>