[css-grid] Typo.

Author: tabatkins

css-grid/Overview.bs

@@ -2109,7 +2109,7 @@ Line-based Placement: the 'grid-row-start', 'grid-column-start', 'grid-row-end',
 
 		<dt><dfn id='grid-placement-int'><<integer>> && <<custom-ident>>?</dfn>
 		<dd>
-			Contributes the <var>N</var>th <a>grid line</a> to the <a>grid item</a>’s <a>placement</a>
+			Contributes the <var>N</var>th <a>grid line</a> to the <a>grid item</a>’s <a>placement</a>.
 			If a negative integer is given,
 			it instead counts in reverse,
 			starting from the end edge of the <a>explicit grid</a>.