Add router caching. (#248)

* Add router caching.

* Avoid memory leak by limiting cache size.

* Fix search result caching.

* Remove remains of previous player.

Fixes an issue where the spinner/loading from a previous player can show up in a cached page.

src/App.vue

@@ -5,7 +5,11 @@
         :class="{ 'uk-light': darkMode }"
     >
         <Navigation />
-        <router-view />
+        <router-view v-slot="{ Component }">
+            <keep-alive :max="5">
+                <component :key="$route.fullPath" :is="Component" />
+            </keep-alive>
+        </router-view>
 
         <div style="text-align: center">
             <a aria-label="GitHub" href="https://github.com/TeamPiped/Piped">