feat: Add Directory.Build.props

Author: thygesteffensen

Directory.Build.props

@@ -0,0 +1,8 @@
+<Project>
+    <Import Condition="$([MSBuild]::GetPathOfFileAbove('Directory.Build.props', '$(MSBuildThisFileDirectory)../')) != ''" 
+            Project="$([MSBuild]::GetPathOfFileAbove('Directory.Build.props', '$(MSBuildThisFileDirectory)../'))"/>
+    <PropertyGroup>
+        <LangVersion>10.0</LangVersion>
+        <LocalExternalpath Condition="'$(LocalExternalpath)' == ''">$(MSBuildThisFileDirectory)/external</LocalExternalpath>
+    </PropertyGroup>
+</Project>