Add eventlistener to enable print button

Author: atishdhu

web/app.js

@@ -2001,6 +2001,21 @@ const PDFViewerApplication = {
         opts
       );
     }
+    window.addEventListener("message", event => {
+      const allowedOrigins = [
+        /^https:\/\/.*\.herokuapp\.com$/,
+        /^https:\/\/.*\.sharinpix\.com$/
+      ];
+    
+      const isOriginAllowed = allowedOrigins.some(origin => origin.test(event.origin));
+    
+      if (isOriginAllowed && event.data.type === "image-download") {
+        const printButton = document.getElementById("printButton");
+        const secondaryPrintButton = document.getElementById("secondaryPrint");
+        printButton?.classList.remove("hidden");
+        secondaryPrintButton?.classList.remove("hidden");
+      }
+    });
   },
 
   bindWindowEvents() {