make sure ActionView::Rendering is included in ActionController::API

[msimonborg]

per #405 , this patch should fix rendering issues I and others have been having in Rails 5+

I'm not sure how to reproduce the issue, as it probably requires loading a dummy app and there could be dependencies or configurations that are causing it.

But I wrote a regression test to check that it works, and it works in the app that has been causing me problems. You can break the test by commenting out include ActionView::Rendering in jbuilder/railtie.rb

[rails-bot]

Thanks for the pull request, and welcome! The Rails team is excited to review your changes, and you should hear from @rwz (or someone else) soon.

If any changes to this PR are deemed necessary, please add them as extra commits. This ensures that the reviewer can see what has changed since they last reviewed the code. Due to the way GitHub handles out-of-date commits, this should also make it reasonably obvious what issues have or haven't been addressed. Large or tricky changes may require several passes of review and changes.

Please see the contribution instructions for more information.