feat(A1): fix name of injection tactic and extend description
feat(A1): fix name of injection tactic and extend description

soonhokong/lean-tutorial,Hodapp87/cs6460_project,soonhokong/lean-tutorial,leanprover/tutorial,avigad/tutorial,Hodapp87/cs6460_project,soonhokong/lean-tutorial,leanprover/tutorial,avigad/tutorial,Hodapp87/cs6460_project,leanprover/tutorial,avigad/tutorial