Fix viewmodel restore on back/forward navigation

* In Firefox, this worked, but also restored it on page reloads
* In Chromium, viewmodel was always reset to the initial state

This patch unifies the behavior to restore the viewmodel, but not if it is in page reload

src/Framework/Framework/Resources/Scripts/dotvvm-base.ts

@@ -69,13 +69,20 @@ export function getStateManager(): StateManager<RootViewModel> { return getCoreS
 
 let initialViewModelWrapper: any;
 
+function isBrowserReload() {
+    return (performance.getEntriesByType("navigation").at(-1) as PerformanceNavigationTiming)?.type == "reload";
+}
+
 export function initCore(culture: string): void {
     if (currentCoreState) {
         throw new Error("DotVVM is already loaded");
     }
 
     // load the viewmodel
-    const thisViewModel = initialViewModelWrapper = JSON.parse(getViewModelStorageElement().value);
+    // if it is back-navigation, we use the viewmodel from history.state
+    const thisViewModel = initialViewModelWrapper =
+        (isBrowserReload() ? null : history.state?.viewModel) ??
+        JSON.parse(getViewModelStorageElement().value);
 
     resourceLoader.registerResources(thisViewModel.renderedResources)
 
@@ -125,7 +132,7 @@ const getViewModelStorageElement = () =>
 
 function persistViewModel() {
     const viewModel = getState()
-    const persistedViewModel = { ...initialViewModelWrapper, viewModel };
-
-    getViewModelStorageElement().value = JSON.stringify(persistedViewModel);
+    history.replaceState({ viewModel: { ...initialViewModelWrapper, viewModel } }, "")
+    // avoid storing the viewmodel hidden field, as Firefox would also reuse it on page reloads
+    getViewModelStorageElement()?.remove()
 }