Add selectrum branch for SPC-* symbol search

other +default/search-... convenience methods already support
Selectrum explicitly, so perhaps there's a good reason not to
do the same for +default/search-project-for-symbol-at-point?

modules/config/default/autoload/search.el

@@ -75,6 +75,8 @@ If prefix ARG is set, prompt for a known project to search from."
            (+ivy/project-search nil symbol))
           ((featurep! :completion helm)
            (+helm/project-search nil symbol))
+          ((featurep! :completion selectrum)
+           (+selectrum/project-search nil symbol))
           ((rgrep (regexp-quote symbol))))))
 
 ;;;###autoload