issue #85 - Cancel button in popup is generating valueSelected event

Change the click hander to close the popup window rather than dispatch
a valueSelected event.

Also since issue #68 put the button in a form, set its type=button so
it doesn't become a submit button by accident. Even if it was a submit
button, the form has no action so it would do nothing but....

From looking at the valueSelected method, I don't think I need to do
any cleanup and can just close the window.

Author: John P. rouillard

html/classhelper.js

@@ -761,12 +761,9 @@ class ClassHelper extends HTMLElement {
 
         const cancel = document.createElement("button");
         cancel.textContent = ClassHelper.translations["cancel"];
+        cancel.setAttribute('type', 'button');
         cancel.addEventListener("click", () => {
-            this.dispatchEvent(new CustomEvent("valueSelected", {
-                detail: {
-                    value: preview.value
-                }
-            }));
+            this.popupRef.close();
         });
 
         const apply = document.createElement("button");