Include winsparkle-tool in nuget package

Add the tool to tools subdirectory.

Also add a $(WinSparkleTool) MSBuild property pointing to it.

Author: vslavik

nuget/WinSparkle.nuspec

@@ -22,7 +22,9 @@
         <file src="..\x64\Release\WinSparkle.lib" target="build\native\x64\" />
         <file src="..\ARM64\Release\WinSparkle.dll" target="build\native\ARM64\" />
         <file src="..\ARM64\Release\WinSparkle.lib" target="build\native\ARM64\" />
+        <file src="..\ARM64\Release\winsparkle-tool.exe" target="tools" />
         <file src="WinSparkle.targets" target="build\native\" />
+        <file src="WinSparkle.props" target="build" />
         <file src="..\*.md" target="" />
         <file src="..\COPYING" target="COPYING" />
     </files>

nuget/WinSparkle.props

@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="utf-8"?>
+<Project ToolsVersion="12.0" DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+  <PropertyGroup>
+    <WinSparkleTool>$(MSBuildThisFileDirectory)..\tools\winsparkle-tool.exe</WinSparkleTool>
+  </PropertyGroup>
+</Project>