Adding doc comment

ignite-template.js

@@ -2048,6 +2048,7 @@ class list extends IgniteTemplate {
  */
 class slot extends IgniteTemplate {
     /**
+     * Creates a new slot with the element who's children will be injected.
      * @param {IgniteElement} element The parent IgniteElement that this slot is for.
      */
     constructor(element) {