Dara: Make centred images aligned centred if they're smaller than the available space. See #376.

dara/blocks.css

@@ -47,6 +47,12 @@ p.has-drop-cap:not(:focus)::first-letter {
 	display: block;
 }
 
+.wp-block-image .aligncenter img {
+	display: block;
+	margin-left: auto;
+	margin-right: auto;
+}
+
 /* Gallery */
 
 .wp-block-gallery {