Add netcoreapp3.1 target to nuget package

From #19, targeting only netcore3.0 might be a problem when only the 3.1 SDK is installed.
The plugin can be compiled with both SDKs and only 3.1 is LTS so it's as good a time as any to start targeting the newer version.

Madd0.AzureStorageDriver/Madd0.AzureStorageDriver.csproj

@@ -1,6 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk.WindowsDesktop">
   <PropertyGroup>
-    <TargetFrameworks>netcoreapp3.0;net46</TargetFrameworks>
+    <TargetFrameworks>netcoreapp3.0;netcoreapp3.1;net46</TargetFrameworks>
     <LangVersion>latest</LangVersion>
     <UseWpf>true</UseWpf>
     <AssemblyName>Madd0.AzureStorageDriver</AssemblyName>
@@ -27,7 +27,7 @@
     <SymbolPackageFormat>snupkg</SymbolPackageFormat>
   </PropertyGroup>
 
-  <PropertyGroup Condition="'$(TargetFramework)' == 'netcoreapp3.0'">
+  <PropertyGroup Condition="'$(TargetFramework)' != 'net46'">
     <DefineConstants>NETCORE</DefineConstants>
   </PropertyGroup>
 
@@ -45,7 +45,7 @@
     <Reference Include="PresentationFramework" />
   </ItemGroup>
 
-  <ItemGroup Condition="'$(TargetFramework)' == 'netcoreapp3.0'">
+  <ItemGroup Condition="'$(TargetFramework)' != 'net46'">
     <PackageReference Include="Microsoft.Azure.Cosmos.Table">
       <Version>1.0.5</Version>
     </PackageReference>
@@ -86,7 +86,7 @@
     </Compile>
   </ItemGroup>
 
-  <Target Name="PostBuild1" AfterTargets="PostBuildEvent" Condition="'$(TargetFramework)' == 'netcoreapp3.0'">
+  <Target Name="PostBuild1" AfterTargets="PostBuildEvent" Condition="'$(TargetFramework)' == 'netcoreapp3.1'">
     <Exec Command="xcopy /i/y/s &quot;$(TargetDir)*.*&quot; &quot;%25LocalAppData%25\\LINQPad\\Drivers\\DataContext\\NetCore\\$(TargetName)&quot;" />
   </Target>