Add @kind to deferinloop.ql

Required to use this query with the CodeQL CLI

Author: sampart

ql/examples/snippets/deferinloop.ql

@@ -3,6 +3,7 @@
  * @description A deferred statement in a loop will not execute until the end of the function.
  *              This can lead to unintentionally holding resources open like file handles or database transactions.
  * @id go/examples/deferinloop
+ * @kind problem
  * @tags defer
  *       nesting
  */