Adds Date response header. Fixes #1863 (#1866)

Author: jwoertink

src/lucky/text_response.cr

@@ -28,6 +28,7 @@ class Lucky::TextResponse < Lucky::Response
     end
     context.response.content_type = content_type
     context.response.status_code = status
+    context.response.headers.add "Date", HTTP.format_time(Time.utc)
     gzip if should_gzip?
     context.response.print(body) if should_print?
   rescue e : IO::Error