[feat] search on category select without JS

Co-authored-by: Alexandre Flament <alex@al-f.net>

searx/settings.yml

@@ -123,6 +123,9 @@ ui:
   theme_args:
     # style of simple theme: auto, light, dark
     simple_style: auto
+  # Perform search immediately if a category selected.
+  # Disable to select multiple categories at once and start the search manually.
+  search_on_category_select: true
 
 # Lock arbitrary settings on the preferences page.  To find the ID of the user
 # setting you want to lock, check the ID of the form on the page "preferences".