Web: Allow navigating to a page on launch with URL argument

www/assets/js/main.js

@@ -204,6 +204,28 @@ if (getStorage("analytics") !== "false") {
 }
 
 
+document.title = SETTINGS.branding.apptitle;
+
+/**
+ * Open the page set in the startpage URL parameter.
+ * @returns {Boolean} true if navigated to a set page, false if app should open something else.
+ */
+function openStartpageURLArg() {
+    try {
+        var urlParams = new URLSearchParams(window.location.search);
+        if (urlParams.has("startpage")) {
+            var startpage = urlParams.get("startpage");
+            if (startpage == "") {
+                return false;
+            }
+            router.navigate("/" + startpage);
+            return true;
+        }
+    } catch (ex) {
+    }
+    return false;
+}
+
 if (setup) {
     router.navigate("/home");
 } else {
@@ -212,4 +234,5 @@ if (setup) {
         pushState: false
     });
 }
-document.title = SETTINGS.branding.apptitle;
+
+openStartpageURLArg();