added BusyOverlay documentation

Author: Michal Diviš

docs/js/AppViewModel.js

@@ -16,7 +16,7 @@ function AppViewModel(contentDivId, drawer) {
     self.documentationItems = [
         new DocumentationItem('appbar', 'App bar', 'https://raw.githubusercontent.com/spiegelp/MaterialDesignExtensions/master/screenshots/MaterialWindow.png', 'snippets/documentation/appbar.html'),
         new DocumentationItem('autocomplete', 'Autocomplete', 'https://raw.githubusercontent.com/spiegelp/MaterialDesignExtensions/master/screenshots/Autocomplete.png', 'snippets/documentation/autocomplete.html'),
-        new DocumentationItem('busyoverlay', 'Busy overlay', null, 'snippets/documentation/busyoverlay.html'),
+        new DocumentationItem('busyoverlay', 'Busy overlay', 'https://raw.githubusercontent.com/spiegelp/MaterialDesignExtensions/master/screenshots/BusyOverlay.png', 'snippets/documentation/busyoverlay.html'),
         new DocumentationItem('filesystemcontrols', 'File system controls', 'https://raw.githubusercontent.com/spiegelp/MaterialDesignExtensions/master/screenshots/OpenFileControl1.png', 'snippets/documentation/filesystemcontrols.html'),
         new DocumentationItem('gridlist', 'Grid list', 'https://raw.githubusercontent.com/spiegelp/MaterialDesignExtensions/master/screenshots/GridList.png', 'snippets/documentation/gridlist.html'),
         new DocumentationItem('materialwindow', 'Material window', 'https://raw.githubusercontent.com/spiegelp/MaterialDesignExtensions/master/screenshots/MaterialWindow.png', 'snippets/documentation/materialwindow.html'),

docs/snippets/documentation/busyoverlay.html

@@ -1,4 +1,85 @@
 <div>
     <h1>Busy overlay</h1>
-    Documentation under construction
+    <p>
+        The following predefined styles are available:
+        <ul>
+            <li><code>MaterialBusyOverlayCircular</code></li>
+            <li><code>MaterialBusyOverlayCircularProgress</code></li>
+            <li><code>MaterialBusyOverlayLinear</code></li>
+            <li><code>MaterialBusyOverlayLinearProgress</code></li>
+        </ul>
+    </p>
+
+    <h2>Screenshots</h2>
+    <img src="https://raw.githubusercontent.com/spiegelp/MaterialDesignExtensions/master/screenshots/BusyOverlay.png" alt="Busy overlay" />
+
+    <h2>Code example</h2>
+   
+    <p>Busy overlay control</p>
+    <pre class="language-markup"><code class="language-markup">
+&lt;mde:BusyOverlay IsBusy="{Binding Path=IsBusy}" 
+    Progress="{Binding Path=Progress}" 
+    Style="{StaticResource MaterialBusyOverlayCircular}" />
+    </code></pre>
+
+    <p>Busy overlay show and progress bindings</p>
+    <pre class="language-markup"><code class="language-markup">
+public class BusyOverlayViewModel : ViewModel
+{
+    private bool _isBusy;
+    public bool IsBusy
+    {
+        get => _isBusy;
+        set
+        {
+            _isBusy = value;
+            OnPropertyChanged(nameof(IsBusy));
+        }
+    }
+
+    private int _progress;
+    public int Progress
+    {
+        get => _progress;
+        set
+        {
+            _progress = value;
+            OnPropertyChanged(nameof(Progress));
+        }
+    }
+
+    public BusyOverlayViewModel() : base()
+    {
+        _isBusy = false;
+        _progress = 0;
+    }
+
+    public async Task BeBusyAsync()
+    {
+        try
+        {
+            Progress = 0;
+            IsBusy = true;
+
+            //Simulate work and update progress
+            await Task.Run(async () =>
+            {
+                int progress = 0;
+
+                while (progress < 100)
+                {
+                    await Task.Delay(250);
+
+                    progress += 10;
+                    Progress = progress;
+                }
+            });
+        }
+        finally
+        {
+            IsBusy = false;
+        }
+    }
+}
+    </code></pre>
 </div>