nav: add history entry only once onload

reloading the page always added a history entry breaking back
button functionality.

fixed by only adding a history entry on load if the history is
empty, so that reloads will not add the same entry over and over
again.

src/main.ts

@@ -216,7 +216,11 @@ const route = (path: string) => {
 
 // onload
 route(location.pathname);
-history.pushState({}, '', location.pathname);
+
+// only push a new entry if there is no history onload
+if (!history.length) {
+  history.pushState({}, '', location.pathname);
+}
 
 window.addEventListener('popstate', (event) => {
   route(location.pathname);