Only toggle sidebar if it is closed (#305)

We were toggling the sidebar regardless of whether it was open or closed.
This caused the back button to close the sidebar on the desktop instead
of opening it (because it was already open).

app/assets/javascripts/application.js

@@ -15,6 +15,6 @@
 
 window.addEventListener("turbolinks:load", () => {
   if (window.matchMedia("(min-width: 768px)").matches) {
-    document.querySelector("#sidebar summary").click();
+    document.querySelector("#sidebar details:not(open) summary")?.click();
   }
 });