Build a package version for net461

This will be resolved by NuGet for .NET Framework 4.6.1 upward, and is
equivalent to the netstandard2.0 package version.

Author: alastairs

src/Serilog.Settings.Configuration/Serilog.Settings.Configuration.csproj

@@ -4,7 +4,7 @@
     <Description>Microsoft.Extensions.Configuration (appsettings.json) support for Serilog.</Description>
     <VersionPrefix>3.0.0</VersionPrefix>
     <Authors>Serilog Contributors</Authors>
-    <TargetFrameworks>netstandard2.0;net451</TargetFrameworks>
+    <TargetFrameworks>netstandard2.0;net451;net461</TargetFrameworks>
     <TreatWarningsAsErrors>true</TreatWarningsAsErrors>
     <GenerateDocumentationFile>true</GenerateDocumentationFile>
     <AssemblyName>Serilog.Settings.Configuration</AssemblyName>
@@ -29,7 +29,7 @@
     <PackageReference Include="Microsoft.Extensions.Options.ConfigurationExtensions" Version="1.1.2" />
   </ItemGroup>
 
-  <ItemGroup Condition="'$(TargetFramework)' == 'netstandard2.0'">
+  <ItemGroup Condition="('$(TargetFramework)' == 'netstandard2.0') Or ('$(TargetFramework)' == 'net461')">
     <PackageReference Include="Microsoft.Extensions.Configuration.Abstractions" Version="2.0.1" />
     <PackageReference Include="Microsoft.Extensions.Options.ConfigurationExtensions" Version="2.0.0" />
   </ItemGroup>