drop gridjs (TracksOverview Actions will need to be re-implemented)

src/App.svelte

@@ -1,5 +1,4 @@
 <script>
-  import "gridjs/dist/theme/mermaid.css";
   import { Route, router } from "tinro";
   router.subscribe((routeInfo) => {
     window.scrollTo(0, 0);