Add failure message for clipboard copy

output/main.js

@@ -295,7 +295,11 @@ function hideElementByID(id) {
  * @param {string} [toastText] - Text shown by toast.
  */
 function copyToClipboard(text, toastText = JOIN_URL_PASTE) {
-	navigator.clipboard.writeText(text);
+	if (typeof navigator.clipboard !== "undefined") {
+		navigator.clipboard.writeText(text);
+	} else {
+		toastText = "Can not copy to clipboard in insecure context.";
+	}
 
 	// Find snackbar element
 	const snackbar = dom.snackbar();