autodoc: Add / as an alternative search key

Per Discord discussion. Motivation: `/` is now the de facto standard for initating search on webpages.

lib/docs/main.js

@@ -4031,6 +4031,7 @@ function addDeclToSearchResults(decl, declIndex, modNames, item, list, stack) {
       case "Esc":
         onEscape(ev);
         break;
+      case "/":
       case "s":
         if (domHelpModal.classList.contains("hidden")) {
           if (ev.target == domSearch) break;