[css-grid] grid and grid-template are animatable

'grid-template-columns' and 'grid-template-rows', are animatable,
as simple lists of length, percentage, or calc.
https://drafts.csswg.org/css-grid/#propdef-grid-template-columns

Thus the shorthands 'grid' and 'grid-template'
https://drafts.csswg.org/css-grid/#propdef-grid
https://drafts.csswg.org/css-grid/#propdef-grid-template
can also animate.

resolves w3c#1794

Author: ericwilligers

css-grid/Overview.bs

@@ -1959,6 +1959,7 @@ Explicit Grid Shorthand: the 'grid-template' property</h3>
 	Percentages: see individual properties
 	Media: visual
 	Computed value: see individual properties
+	Animatable: see individual properties
 	</pre>
 
 	The 'grid-template' property is a <a>shorthand</a> for setting
@@ -2330,6 +2331,7 @@ Grid Definition Shorthand: the 'grid' property</h3>
 	Percentages: see individual properties
 	Media: visual
 	Computed value: see individual properties
+	Animatable: see individual properties
 	</pre>
 
 	The 'grid' property is a <a>shorthand</a> that sets