Add Davey Newhall as a maintainer
As demonstrated by the commit history, Davey has been consistently
contributing to Grid for quite a while.
-* @agunde406 @chenette @davececchi @dcmiddle @dplumb94 @eloaverona @jsmitchell @peterschwarz @rberg2 @rbuysse @RyanLassigBanks @shannynalayna @vaporos
+* @agunde406 @chenette @davececchi @dcmiddle @dnewh @dplumb94 @eloaverona @jsmitchell @peterschwarz @rberg2 @rbuysse @RyanLassigBanks @shannynalayna @vaporos
