fix: AvaloniaPublicKey.props file name typo

Directory.Build.props

@@ -1,5 +1,5 @@
 <Project>
-  <Import Project="$(MSBuildThisFileDirectory)/build/AvaloniaPrublicKey.props"/>
+  <Import Project="$(MSBuildThisFileDirectory)/build/AvaloniaPublicKey.props"/>
   <PropertyGroup>
       <PackageOutputPath Condition="'$(PackageOutputPath)' == ''">$(MSBuildThisFileDirectory)build-intermediate/nuget</PackageOutputPath>
       <AvaloniaPreviewerNetCoreToolPath>$(MSBuildThisFileDirectory)\src\tools\Avalonia.Designer.HostApp\bin\$(Configuration)\netcoreapp2.0\Avalonia.Designer.HostApp.dll</AvaloniaPreviewerNetCoreToolPath>