Ruby 2.7. Add spec for beginless range syntax

Author: andrykonchin

language/range_spec.rb

@@ -16,4 +16,11 @@
       eval("(1...)").should == Range.new(1, nil, true)
     end
   end
+
+  ruby_version_is "2.7" do
+    it "creates beginless ranges" do
+      eval("(..1)").should == Range.new(nil, 1)
+      eval("(...1)").should == Range.new(nil, 1, true)
+    end
+  end
 end