Add color for inactive title-bar (#84)

* Add color for inactive title-bar

* add docs

Co-authored-by: xFly.Xie <Fly.Xie@grandsys.com>

docs/index.html.ejs

@@ -554,6 +554,18 @@
               <button aria-label="Close"></button>
             </div>
           </div>
+        `) %>
+		<p>
+          You can make a title bar "inactive" by adding <code>inactive</code> class,
+		  useful when making more than one window.
+        </p>
+		 <%- example(`
+          <div class="title-bar inactive">
+            <div class="title-bar-text">An inactive title bar</div>
+            <div class="title-bar-controls">
+              <button aria-label="Close"></button>
+            </div>
+          </div>
         `) %>
       </div>
     </section>