added VisualStudioToolsManifest to show controls in Toolbox (#1729)

Author: Mrxx99

MaterialDesignThemes.Wpf/VisualStudioToolsManifest.xml

@@ -0,0 +1,22 @@
+<FileList>
+  <File Reference = "MaterialDesignThemes.Wpf.dll">
+    <ToolboxItems VSCategory="MaterialDesignThemes.Wpf" BlendCategory="MaterialDesignThemes.Wpf">
+      <Item Type="MaterialDesignThemes.Wpf.Badged" />
+      <Item Type="MaterialDesignThemes.Wpf.Card" />
+      <Item Type="MaterialDesignThemes.Wpf.Chip" />
+      <Item Type="MaterialDesignThemes.Wpf.Clock" />
+      <Item Type="MaterialDesignThemes.Wpf.ColorPicker" />
+      <Item Type="MaterialDesignThemes.Wpf.ColorZone" />
+      <Item Type="MaterialDesignThemes.Wpf.DataGridComboBoxColumn" />
+      <Item Type="MaterialDesignThemes.Wpf.DataGridTextColumn" />
+      <Item Type="MaterialDesignThemes.Wpf.DialogHost" />
+      <Item Type="MaterialDesignThemes.Wpf.DrawerHost" />
+      <Item Type="MaterialDesignThemes.Wpf.Flipper" />
+      <Item Type="MaterialDesignThemes.Wpf.PackIcon" />
+      <Item Type="MaterialDesignThemes.Wpf.PopupBox" />
+      <Item Type="MaterialDesignThemes.Wpf.RatingBar" />
+      <Item Type="MaterialDesignThemes.Wpf.Snackbar" />
+      <Item Type="MaterialDesignThemes.Wpf.TimePicker" />
+    </ToolboxItems>
+  </File>
+</FileList>

MaterialDesignThemes.nuspec

@@ -28,5 +28,6 @@
     <file src="MaterialDesignThemes.Wpf\bin\$configuration$\netcoreapp3.1\MaterialDesignThemes.Wpf.*" target="lib\netcoreapp3.1" exclude="**\*.json" />
     <file src="MaterialDesignThemes.Wpf\Resources\Roboto\*.ttf" target="build\Resources\Roboto" />
     <file src="MaterialDesignThemes.Wpf\MaterialDesignThemes.targets" target="build" />
+    <file src="MaterialDesignThemes.Wpf\VisualStudioToolsManifest.xml" target="tools"/>
   </files>
 </package>