This adds a new command `search', bound by default to `s', that prompts for a query and loads and consult the ``oracle'' (the search engine) using default_search_engine (which will be made customizable.) It also temporarly supports only gemini URLs. Feature requested by -fab-, thanks!

turns out telescope is not ready to generate certificate in the ui process, a separate helper will be added for it, so remove this option for now.

Two stores are not a good idea to handle all the edge-cases since telescope supports certificates (or absence of these) per-session.

This way we can improve unload-certificate prompt. While here, move the cert handling in make_request().