Rename docs search page to avoid clashing with Sphinx search UI

The search.py API page was generated as search.html, which collides with
Sphinx's reserved built-in search page (also search.html) and was overwritten,
losing the module docs. Rename the topic page to searching.rst so the search
module is documented at searching.html while search.html remains the search UI.

Author: dmeoli

docs/index.rst

@@ -13,7 +13,7 @@ chapter numbering; the unsuffixed modules track the 3rd edition.
    :caption: API reference
 
    agents
-   search
+   searching
    games
    csp
    logic