Add search control to several experiments

[prushforth]

Not a complete solution, by any means. There should be a few explicit custom search handler experiments that render features. I think that would help expose some requirements or limitations of the current implementation.

Other things tbd:

• RTL text should be respected by the search text entry
• the Feature Index should get populated with search hits, or something along those lines (search hits should become features in some cases such as this).