Update getting-started.html

Added missing  "?" in ` <?xml version="1.0">`

Author: stefonarch

getting-started.html

@@ -173,7 +173,7 @@ <h2 id="step-2---add-some-items-to-the-root-menu">Step 2 - Add some
 See <a
 href="https://github.com/labwc/labwc/blob/master/docs/menu.xml">docs/menu.xml</a>
 for inspiration, or use the simple example below</p>
-<pre><code>&lt;?xml version=&quot;1.0&quot;&gt;
+<pre><code>&lt;?xml version=&quot;1.0&quot;?&gt;
 
 &lt;openbox_menu&gt;
 &lt;menu id=&quot;root-menu&quot; label=&quot;&quot;&gt;
@@ -247,4 +247,4 @@ <h2 id="step-5---install-some-themes-for-server-side-decorations">Step 5
 </section>
 </main>
 </body>
-</html>
+</html>