elevate top bar on scroll

src/components/TopBar.vue

 <template>
-        <v-app-bar app class = "top-bar" dense dark color="primary">
+        <v-app-bar elevate-on-scroll app class = "top-bar" dense dark color="primary">
       <div class="beta" :title="release">{{version_label}}</div>
       <v-spacer/>
       <v-toolbar-items v-if="false">