User documentation: image layout improved

plugins/org.yakindu.sct.doc.user/css/custom.css

@@ -112,4 +112,11 @@
 	filter: alpha(opacity =   40);
 	background: url("../img/player_play.png") center center no-repeat;
 	z-index: 10;
-}
+}
+
+img {
+    max-width: 94%;
+    height: auto;
+    margin-left: 3%;
+    display: block;
+}