Examples: Added README into the Visual Studio solution to people are less likely to miss it.

examples/directx11_example/directx11_example.vcxproj

@@ -150,6 +150,9 @@
     <ClCompile Include="imgui_impl_dx11.cpp" />
     <ClCompile Include="main.cpp" />
   </ItemGroup>
+  <ItemGroup>
+    <None Include="..\README.txt" />
+  </ItemGroup>
   <Import Project="$(VCTargetsPath)\Microsoft.Cpp.targets" />
   <ImportGroup Label="ExtensionTargets">
   </ImportGroup>