docs(demo): update description text

Author: netil

demo/index.html

@@ -103,7 +103,7 @@ <h2 class="sidebar-brand">billboard.js</h2>
                 <option value="dark">dark</option>
                 <option value="insight">insight</option>
                 <option value="graph">graph</option>
-                <option value="modern">modern</option>
+<option value="modern">modern</option>
             </select>
         </form>
         <p id="launch" title="To open as new window, hold the 'Alt(Win)/option(Mac)' key while clicking.">
@@ -130,8 +130,7 @@ <h2 id="title"></h2>
                             <div class="chart_area">
                                 <h1>billboard.js examples</h1>
                                 <p>
-                                    Discover all <span class="item_count"></span> examples!
-                                    <!-- by navigating <span class="by_text"></span>. -->
+                                    Explore all <span class="item_count"></span> examples from the left menu list.
                                 </p>
 
                                 <h4>Supported chart types</h4>