feat: Object#sleep, Object#sleep_ms を定義 (#48)

* feat: `Object#sleep`, `Object#sleep_ms` を定義

* chore: テストを追加

Author: tufusa

core/object.rbs

@@ -84,4 +84,8 @@ class Object < BasicObject
   alias self.inspect self.to_s
 
   def loop: () { () -> void } -> bot
+
+  def sleep: (Integer | Float sec) -> Integer
+
+  def sleep_ms: (Integer ms) -> Integer
 end

test/object.rb

@@ -128,4 +128,9 @@ module TestMod end
 
 loop { puts }
 
+sleep 1
+sleep 1.0
+
+sleep_ms 1000
+
 # rubocop:enable all