Add firefox for fallback as well

Author: phoneticallySAARTHaK

src/script.js

@@ -173,7 +173,9 @@ function needsFallback() {
   const isAppleDevice = /MacIntel|iPhone|iPad|iPod/i.test(platform);
   const isSafari = /^((?!chrome|android).)*safari/i.test(userAgent);
 
-  return isAppleDevice || isSafari;
+  const isFirefox = navigator.userAgent.toLowerCase().indexOf("firefox") > -1;
+
+  return isAppleDevice || isSafari || isFirefox;
 }
 
 function handleFallbackSetup() {
@@ -184,7 +186,7 @@ function handleFallbackSetup() {
 
   const p = document.createElement("p");
   p.innerHTML =
-    "If you are using an Apple Device, the blue border may not show up on the image. <br> " +
+    "If you are using an Apple Device or Firefox, the image not be generated properly. <br> " +
     "You can click the 'Generate fallback' button below to get the server generated image. <br> " +
     "Note that it can take a couple of seconds to load. <br>" +
     "<strong> This is a limited, temporary fix. Size has no effect.</strong>";