Update contributor name in .mailmap

Author: boringcactus

.mailmap

@@ -155,6 +155,7 @@ Matt Brubeck <mbrubeck@limpet.net> <mbrubeck@cs.hmc.edu>
 Matthew Auld <matthew.auld@intel.com>
 Matthew McPherrin <matthew@mcpherrin.ca> <matt@mcpherrin.ca>
 Matthijs Hofstra <thiezz@gmail.com>
+Melody Horn <melody@boringcactus.com> <mathphreak@gmail.com>
 Michael Williams <m.t.williams@live.com>
 Michael Woerister <michaelwoerister@posteo> <michaelwoerister@gmail>
 Mickaël Raybaud-Roig <raybaudroigm@gmail.com> m-r-r <raybaudroigm@gmail.com>