Added selectedOptions Property To HTMLSelectElement

Fixes microsoft/TypeScript#6096

Author: crash-dive

baselines/dom.generated.d.ts

@@ -6170,6 +6170,7 @@ interface HTMLSelectElement extends HTMLElement {
       * Returns whether an element will successfully validate based on forms validation rules and constraints.
       */
     willValidate: boolean;
+    selectedOptions: HTMLCollection;
     /**
       * Adds an element to the areas, controlRange, or options collection.
       * @param element Variant of type Number that specifies the index position in the collection where the element is placed. If no value is given, the method places the element at the end of the collection.

inputfiles/addedTypes.json

@@ -290,5 +290,11 @@
         "interface": "AudioContext",
         "name": "state",
         "type": "string"
+    },
+    {
+        "kind": "property",
+        "interface": "HTMLSelectElement",
+        "name": "selectedOptions",
+        "type": "HTMLCollection"
     }
 ]