Allow running repls on cover page

Description of the problem (please keep it simple and short):
Now that you may only run repls by forking them, even HTML repls, which do not even have a backend, are only viewable by forking. I believe that HTML repls should be shown on the cover page if you click a run button.
Explain what you were trying to do:
Trying to view a trending repl.
What areas or features are involved?
Repl cover page