New: Add release date sort option to book index view

Fixes #1403

frontend/src/Book/Details/BookDetailsHeader.js

@@ -149,6 +149,8 @@ class BookDetailsHeader extends Component {
             </div>
 
             <div className={styles.detailsLabels}>
+              {
+                releaseDate &&
                   <Label
                     className={styles.detailsLabel}
                     size={sizes.LARGE}
@@ -164,6 +166,7 @@ class BookDetailsHeader extends Component {
                       }
                     </span>
                   </Label>
+              }
 
               <Label
                 className={styles.detailsLabel}

frontend/src/Book/Index/Menus/BookIndexSortMenu.js

@@ -46,6 +46,15 @@ function BookIndexSortMenu(props) {
           Author, Title
         </SortMenuItem>
 
+        <SortMenuItem
+          name="releaseDate"
+          sortKey={sortKey}
+          sortDirection={sortDirection}
+          onPress={onSortSelect}
+        >
+          Release Date
+        </SortMenuItem>
+
         <SortMenuItem
           name="qualityProfileId"
           sortKey={sortKey}