[ruby/time] Make Time friendly to Ractor

https://github.com/ruby/time/commit/c784e4f166

lib/time.rb

@@ -1,4 +1,5 @@
 # frozen_string_literal: true
+# shareable_constant_value: literal
 
 require 'date'
 

test/test_time.rb

@@ -62,6 +62,13 @@ class TestTimeExtension < Test::Unit::TestCase # :nodoc:
     assert_equal(true, t.utc?)
   end
 
+  if defined?(Ractor)
+    def test_rfc2822_ractor
+      actual = Ractor.new { Time.rfc2822("Fri, 21 Nov 1997 09:55:06 -0600") }.take
+      assert_equal(Time.utc(1997, 11, 21, 9, 55, 6) + 6 * 3600, actual)
+    end
+  end
+
   def test_encode_rfc2822
     t = Time.utc(1)
     assert_equal("Mon, 01 Jan 0001 00:00:00 -0000", t.rfc2822)