Add target for .net standard 2.0

Author: Vadim Hatsura

src/Serilog.Sinks.File/Serilog.Sinks.File.csproj

@@ -4,7 +4,7 @@
     <Description>Write Serilog events to text files in plain or JSON format.</Description>
     <VersionPrefix>4.0.1</VersionPrefix>
     <Authors>Serilog Contributors</Authors>
-    <TargetFrameworks>net45;netstandard1.3</TargetFrameworks>
+    <TargetFrameworks>net45;netstandard1.3;netstandard2.0</TargetFrameworks>
     <GenerateDocumentationFile>true</GenerateDocumentationFile>
     <AssemblyName>Serilog.Sinks.File</AssemblyName>
     <AssemblyOriginatorKeyFile>../../assets/Serilog.snk</AssemblyOriginatorKeyFile>
@@ -48,6 +48,10 @@
     <DefineConstants>$(DefineConstants);OS_MUTEX</DefineConstants>
   </PropertyGroup>
 
+  <PropertyGroup Condition=" '$(TargetFramework)' == 'netstandard2.0' ">
+    <DefineConstants>$(DefineConstants);OS_MUTEX</DefineConstants>
+  </PropertyGroup>
+
   <ItemGroup Condition=" '$(TargetFramework)' == 'netstandard1.3' ">
     <PackageReference Include="System.IO" Version="4.1.0" />
     <PackageReference Include="System.IO.FileSystem" Version="4.0.1" />
@@ -58,4 +62,11 @@
     <PackageReference Include="System.Runtime.InteropServices" Version="4.1.0" />
   </ItemGroup>
 
+  <ItemGroup Condition=" '$(TargetFramework)' == 'netstandard2.0' ">
+    <PackageReference Include="System.IO" Version="4.1.0" />
+    <PackageReference Include="System.IO.FileSystem" Version="4.0.1" />
+    <PackageReference Include="System.IO.FileSystem.Primitives" Version="4.0.1" />
+    <PackageReference Include="System.Text.Encoding.Extensions" Version="4.0.11" />
+    <PackageReference Include="System.Threading.Timer" Version="4.0.1" />
+  </ItemGroup>
 </Project>