Hide the window until loading is done

src-tauri/capabilities/default.json

@@ -18,6 +18,7 @@
     "core:window:allow-start-dragging",
     "core:window:allow-toggle-maximize",
     "core:window:allow-request-user-attention",
+    "core:window:allow-show",
     "core:webview:allow-create-webview-window",
     "fs:default",
     "fs:allow-remove",