add sudoku to mkfile so it will be compiled and installed

Reference: /n/sources/patch/applied/mkfile-addsudoku
Date: Fri Feb 17 18:45:07 CET 2006
Signed-off-by: andrey@lanl.gov

--- /sys/src/games/mkfile	Fri Feb 17 18:44:33 2006
+++ /sys/src/games/mkfile	Fri Feb 17 18:44:31 2006
@@ -15,6 +15,7 @@
 DIRS=\
 	mahjongg\
 	sokoban\
+	sudoku\
 
 4s.$O 5s.$O xs.$O:	xs.h
 $O.4s $O.5s: xs.$O