feat(unixode.sty): add ↑ and ↓
feat(unixode.sty): add ↑ and ↓

soonhokong/lean-tutorial,avigad/tutorial,leanprover/tutorial,avigad/tutorial,soonhokong/lean-tutorial,leanprover/tutorial,Hodapp87/cs6460_project,soonhokong/lean-tutorial,leanprover/tutorial,avigad/tutorial,Hodapp87/cs6460_project,cjmazey/fork_leanprover_tutorial,fpvandoorn/tutorial,cjmazey/fork_leanprover_tutorial,Hodapp87/cs6460_project,cjmazey/fork_leanprover_tutorial,fpvandoorn/tutorial,fpvandoorn/tutorial