Add the player select applet. (#537)

This introduces the somewhat completed version of the Player Select
Applet, allowing users to select either a user or a guest from the UI.
Note: Selecting the guest more then once currently does not work.

closes https://github.com/Ryubing/Ryujinx/issues/532

src/Ryujinx/Ryujinx.csproj

@@ -173,4 +173,10 @@
   <ItemGroup>
     <Folder Include="Assets\Fonts\Mono\" />
   </ItemGroup>
+  <ItemGroup>
+    <Compile Update="UI\Applet\UserSelectorDialog.axaml.cs">
+      <DependentUpon>UserSelectorDialog.axaml</DependentUpon>
+      <SubType>Code</SubType>
+    </Compile>
+  </ItemGroup>
 </Project>