Add standalone file for CSS animations

less/animations.less

@@ -0,0 +1,24 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+@keyframes fadeIn {
+  from {
+    opacity: 0
+  }
+  to {
+    opacity: 1
+  }
+}
+
+@keyframes tabFadeIn {
+  0% {
+    opacity: 0.5
+  }
+  50% {
+    opacity: 0.6
+  }
+  100% {
+    opacity: 0.5
+  }
+}

less/navigationBar.less

@@ -6,18 +6,9 @@
  * Navigation layers
  */
 
+@import "animations.less";
 @import "variables.less";
 
-// Fade In animation for URL bar transitions
-@keyframes fadeIn {
-  from {
-    opacity: 0
-  }
-  to {
-    opacity: 1
-  }
-}
-
 // All platforms - media queries
 @media (max-width: @breakpointNarrowViewport) {
   .loadTime { display: none; }

less/window.less

@@ -2,18 +2,9 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this file,
  * You can obtain one at http://mozilla.org/MPL/2.0/. */
 
+@import "animations.less";
 @import "variables.less";
-@keyframes tabFadeIn {
-  0% {
-    opacity: 0.5
-  }
-  50% {
-    opacity: 0.6
-  }
-  100% {
-    opacity: 0.5
-  }
-}
+
 :root {
   --default-font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Oxygen, Ubuntu, Cantarell, "Fira Sans", "Droid Sans", "Helvetica Neue", sans-serif;
 }