Merge pull request w3c#985 from rachelandrew/gridexamples

[css-grid] Replaced example screenshots with SVG versions

Author: fantasai

css-grid/Overview.bs

@@ -3528,15 +3528,15 @@ Aligning the Grid: the 'justify-content' and 'align-content' properties</h3>
 		</pre>
 
 		<figure>
-			<img src="images/spanned-gap.png"
+			<img src="images/spanned-gap.svg"
 			     alt="Grid with 10px gap and an element spanning all columns.
-			          The sum of the columns is less than the width of the grid container.">
+			          The sum of the columns is less than the width of the grid container." height="426" width="500">
 			<figcaption>Grid before alignment</figure>
 		</figure>
         <figure>
-			<img src="images/spanned-gap-align.png"
+			<img src="images/spanned-gap-align.svg"
 			     alt="Same grid with increased gaps absorbing the excess grid containe width.
-			          The spanning element has grown to accommodate the extra space assigned to the gap it crosses.">
+			          The spanning element has grown to accommodate the extra space assigned to the gap it crosses." height="426" width="500">
 			<figcaption>Grid after alignment</figure>
 		</figure>