Update CODEOWNERS on JE request (#8421)

Author: ddobrigk

CODEOWNERS

@@ -55,7 +55,7 @@
 /PWGMM/UE   @alibuild @aalkin @aortizve
 
 /PWGUD @alibuild @pbuehler @abylinkin @rolavick
-/PWGJE @alibuild @lhavener @maoyx @nzardosh @fjonasALICE @mfasDa
+/PWGJE @alibuild @lhavener @maoyx @nzardosh @fjonasALICE @mfasDa @mhemmer-cern
 /Tools/PIDML @alibuild @saganatt
 /Tools/ML @alibuild @fcatalan92 @fmazzasc
 /Tutorials/PWGCF @alibuild @jgrosseo @saganatt @victor-gonzalez @zchochul