[css-flexbox] Fix typo on line 1621 (w3c#1648)

* Replace example screenshot image with SVG version for Example 22

* [css-grid] Replace example screenshot image with SVG version for Example 22 (fix space conversion issue)

* [css-flexbox] Fix typo in line 1621

Author: Chen Hui Jing

css-flexbox/Overview.bs

@@ -1618,7 +1618,7 @@ Basic Values of 'flex'</h4>
 	<em>This section is informative.</em>
 
 	The list below summarizes the effects of the four 'flex' values
-	that respresent most commonly-desired effects:
+	that represent most commonly-desired effects:
 
 	<dl>
 		<dt id="flex-initial">''flex: initial''