Add ability to use 'shift+delete' to delete torrents in WebUI

Closes #13827.

src/webui/www/private/scripts/client.js

@@ -1225,6 +1225,10 @@ new Keyboard({
         'delete': function(event) {
             deleteFN();
             event.preventDefault();
+        },
+        'shift+delete': (event) => {
+            deleteFN(true);
+            event.preventDefault();
         }
     }
 }).activate();