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
diff --git a/.mailmap b/.mailmap
index da17344..7f640d4 100644
--- a/.mailmap
+++ b/.mailmap
@@ -44,6 +44,7 @@
 Brian Anderson <[email protected]> <[email protected]>
 Brian Dawn <[email protected]>
 Brian Leibig <[email protected]> Brian Leibig <[email protected]>
+Camelid <[email protected]> <[email protected]>
 Carl-Anton Ingmarsson <[email protected]> <[email protected]>
 Carol (Nichols || Goulding) <[email protected]> <[email protected]>
 Carol (Nichols || Goulding) <[email protected]> <[email protected]>