Add types in and around Grammar.rb #1292

Job	Run time
check-misc (head)	6s
steep-check (head)	18s
test-memory (head)	28s
test-ruby (head, master)	5m 50s
test-windows (head)	3m 11s
test-ruby (3.0, master)	5m 39s
ruby-versions / Generate Ruby versions	4s
test (2.5)	22s
test (2.6)	22s
test (2.7)	21s
test (3.0)	11s
test (3.1)	11s
test (3.2)	11s
test (3.3)	14s
test (head)	14s
	17m 42s

Provide feedback