Add missing license comment on a new-ish source file.
Add missing license comment on a new-ish source file.

tgdavies/codeworld,pranjaltale16/codeworld,three/codeworld,parvmor/codeworld,tgdavies/codeworld,google/codeworld,venkat24/codeworld,venkat24/codeworld,google/codeworld,google/codeworld,three/codeworld,alphalambda/codeworld,alphalambda/codeworld,tgdavies/codeworld,parvmor/codeworld,pranjaltale16/codeworld,three/codeworld,pranjaltale16/codeworld,venkat24/codeworld,parvmor/codeworld,alphalambda/codeworld