Add logging package

src/Discord.Net.Core/Discord.Net.Core.csproj

@@ -9,6 +9,7 @@
     <TargetFrameworks Condition=" '$(OS)' != 'Windows_NT' ">netstandard2.0;netstandard2.1</TargetFrameworks>
   </PropertyGroup>
   <ItemGroup>
+    <PackageReference Include="Microsoft.Extensions.Logging.Abstractions" Version="5.0.0" />
     <PackageReference Include="Newtonsoft.Json" Version="12.0.2" />
     <PackageReference Include="System.Collections.Immutable" Version="1.3.1" />
     <PackageReference Include="System.Interactive.Async" Version="4.0.0" />