add netstandard2.1 for AspectCore extensions

Author: WeihanLi

src/WeihanLi.Common.Aspect.AspectCore/WeihanLi.Common.Aspect.AspectCore.csproj

@@ -9,7 +9,7 @@
     <PackageReleaseNotes>
       https://github.com/WeihanLi/WeihanLi.Common/blob/dev/docs/ReleaseNotes.md
     </PackageReleaseNotes>
-    <TargetFramework>netstandard2.0</TargetFramework>
+    <TargetFrameworks>netstandard2.0;netstandard2.1</TargetFrameworks>
   </PropertyGroup>
 
   <ItemGroup>