Add sortBy Last Book Added and Updated to series

client/components/app/BookShelfToolbar.vue

@@ -163,6 +163,14 @@ export default {
           text: this.$strings.LabelAddedAt,
           value: 'addedAt'
         },
+        {
+          text: this.$strings.LabelLastBookAdded,
+          value: 'lastBookAdded'
+        },
+        {
+          text: this.$strings.LabelLastBookUpdated,
+          value: 'lastBookUpdated'
+        },
         {
           text: this.$strings.LabelTotalDuration,
           value: 'totalDuration'

client/strings/en-us.json

@@ -250,6 +250,8 @@
   "LabelItem": "Item",
   "LabelLanguage": "Language",
   "LabelLanguageDefaultServer": "Default Server Language",
+  "LabelLastBookAdded": "Last Book Added",
+  "LabelLastBookUpdated": "Last Book Updated",
   "LabelLastSeen": "Last Seen",
   "LabelLastTime": "Last Time",
   "LabelLastUpdate": "Last Update",