Does the comment contain an acknowledgement (+1)

Property definitions

github $ Comment :: is_ack
	# Does the comment contain an acknowledgement (+1)
	fun is_ack: Bool do
		return body.has("\\+1\\b".to_re) or body.has(":+1:") or body.has(":shipit:")
	end
lib/github/api.nit:841,2--844,4