feat: add localization to admin nav + locale sections

client/components/admin/admin-dashboard.vue

@@ -2,8 +2,8 @@
   v-container(fluid, fill-height)
     v-layout(row wrap)
       v-flex(xs12)
-        .headline.primary--text Dashboard
-        .subheading.grey--text Wiki.js v2 ALPHA Build - NOT FOR PRODUCTION USE
+        .headline.primary--text {{ $t('admin:dashboard.title') }}
+        .subheading.grey--text {{ $t('admin:dashboard.subtitle') }}
 </template>
 
 <script>