Add object-fit polyfill for Edge (#4182)

app/javascript/mastodon/extra_polyfills.js

@@ -1,2 +1,5 @@
 import 'intersection-observer';
 import 'requestidlecallback';
+import objectFitImages  from 'object-fit-images';
+
+objectFitImages();

app/javascript/mastodon/load_polyfills.js

@@ -20,11 +20,12 @@ function loadPolyfills() {
   );
 
   // Latest version of Firefox and Safari do not have IntersectionObserver.
-  // Edge does not have requestIdleCallback.
+  // Edge does not have requestIdleCallback and object-fit CSS property.
   // This avoids shipping them all the polyfills.
   const needsExtraPolyfills = !(
     window.IntersectionObserver &&
-    window.requestIdleCallback
+    window.requestIdleCallback &&
+    'object-fit' in (new Image()).style
   );
 
   return Promise.all([