AUTHORS: add the commit hash as of we counted.
# Authors of mruby (mruby developers)
-## The List of Contributors sorted by number of commits (as of 2021-03-10)
+## The List of Contributors sorted by number of commits (as of 2021-03-10 14f5313)
7235 Yukihiro "Matz" Matsumoto (@matz)*
567 KOBAYASHI Shuji (@shuujii)
