fix(@types/select2): Add missing $.fn.select2 typing

As per bottom of docs at http://select2.github.io/select2/

types/select2/v3/index.d.ts

@@ -168,6 +168,14 @@ interface Select2Plugin {
     (method: 'search'): JQuery;
 
     (options: Select2Options): JQuery;
+
+    /**
+     * Select2 exposes its default options via the $.fn.select2.defaults
+     * object. Properties changed in this object (same properties configurable
+     * through the constructor) will take effect for every instance created
+     * after the change.
+     */
+    defaults: Partial<Select2Options>;
 }
 
 interface JQuery {

types/select2/v3/select2-tests.ts

@@ -1,3 +1,8 @@
+$.extend($.fn.select2.defaults, {
+  width: 'copy',
+  minimumInputLength: 12
+});
+
 $("#e9").select2();
 $("#e2").select2({
     placeholder: "Select a State",