fix(button): icon adjustments in animated button

- Adjusts vertical-align for icons in animated buttons
- Adds support for .ui.animated.icon.button

Author: dutrieux

src/definitions/elements/button.less

@@ -706,15 +706,19 @@
 ---------------*/
 
 .ui.icon.buttons .button,
-.ui.icon.button {
+.ui.icon.button:not(.animated) {
   padding: @verticalPadding @verticalPadding ( @verticalPadding + @shadowOffset );
 }
+.ui.animated.icon.button > .content > .icon,
 .ui.icon.buttons .button > .icon,
 .ui.icon.button > .icon {
   opacity: @iconButtonOpacity;
   margin: 0 !important;
   vertical-align: top;
 }
+.ui.animated.button > .content > .icon {
+  vertical-align: top;
+}
 
 & when (@variationButtonBasic) {
   /*-------------------