Merge pull request #15109 from nextcloud/backport/15107/stable16

[stable16] Add animation-slow var

core/css/css-variables.scss

@@ -41,4 +41,5 @@
 	--font-face: $font-face;
 
 	--animation-quick: $animation-quick;
+	--animation-slow: $animation-slow;
 }

core/css/variables.scss

@@ -82,6 +82,7 @@ $border-radius-pill: 100px !default;
 $font-face: 'Nunito', 'Open Sans', Frutiger, Calibri, 'Myriad Pro', Myriad, sans-serif !default;
 
 $animation-quick: 100ms;
+$animation-slow: 300ms;
 
 // various structure data
 $header-height: 50px;