[css-animations-2] Define animation-timeline with animation type

Author: cdoublev

css-animations-2/Overview.bs

@@ -532,7 +532,7 @@ Computed value: list, each item either a case-sensitive [=css identifier=] or
     the keywords ''single-animation-timeline/none'',
     ''single-animation-timeline/auto''.
 Canonical order: per grammar
-Animatable: no
+Animation Type: not animatable
 </pre>
 
 <pre class=prod>