Fix uppercase PopupInfo class name (#63)

Co-authored-by: Brian Thomas Smith <brian@smith.berlin>

Author: temp4422

popup-info-box-external-stylesheet/main.js

@@ -1,5 +1,5 @@
 // Create a class for the element
-class PopUpInfo extends HTMLElement {
+class PopupInfo extends HTMLElement {
   constructor() {
     // Always call super first in constructor
     super();
@@ -50,4 +50,4 @@ class PopUpInfo extends HTMLElement {
 }
 
 // Define the new element
-customElements.define("popup-info", PopUpInfo);
+customElements.define("popup-info", PopupInfo);