web: Add vue router.

web/src/App.vue

@@ -1,20 +1,11 @@
 <template>
-  <img alt="Vue logo" src="./assets/logo.png" />
-  <HelloWorld msg="Welcome to Your Vue.js + TypeScript App" />
+  <div id="nav">
+    <router-link to="/">Home</router-link> |
+    <router-link to="/about">About</router-link>
+  </div>
+  <router-view />
 </template>
 
-<script lang="ts">
-import { defineComponent } from "vue";
-import HelloWorld from "./components/HelloWorld.vue";
-
-export default defineComponent({
-  name: "App",
-  components: {
-    HelloWorld,
-  },
-});
-</script>
-
 <style lang="scss">
 #app {
   font-family: Avenir, Helvetica, Arial, sans-serif;
@@ -22,6 +13,18 @@ export default defineComponent({
   -moz-osx-font-smoothing: grayscale;
   text-align: center;
   color: #2c3e50;
-  margin-top: 60px;
+}
+
+#nav {
+  padding: 30px;
+
+  a {
+    font-weight: bold;
+    color: #2c3e50;
+
+    &.router-link-exact-active {
+      color: #42b983;
+    }
+  }
 }
 </style>