Add small ease-in-out transition between pages. (#66)

Really makes a big difference than before.

layouts/default.vue

@@ -253,6 +253,16 @@ export default {
 </script>
 
 <style lang="scss">
+.page-enter-active,
+.page-leave-active {
+  transition: ease-in-out 100ms;
+}
+
+.page-enter,
+.page-leave-to {
+  opacity: 0;
+}
+
 .layout {
   background-color: var(--color-bg);
   display: block;