Format: add indentation

added a little indentation

Author: jiangying000

css-grid-1/Overview.bs

@@ -669,12 +669,12 @@ Grid Areas</h3>
 		<pre>
 			/* using the template syntax */
 			#grid  {
-			display: grid;
-			grid-template-areas: ". a"
-			                     "b a"
-			                     ". a";
-			grid-template-columns: 150px 1fr;
-			grid-template-rows: 50px 1fr 50px;
+				display: grid;
+				grid-template-areas: ". a"
+						     "b a"
+						     ". a";
+				grid-template-columns: 150px 1fr;
+				grid-template-rows: 50px 1fr 50px;
 			}
 
 			#item1 { grid-area: a }