[C#] Docs missing netstandard2.0 target support

[daveleek]

Hi, docs mention support for netstandard2.1, net6.0 and net8.0. But not netstandard2.0.

Building the FlatBuffers C# library

The FlatBuffers.csproj project contains multitargeting for .NET Standard 2.1, .NET 6 and .NET 8.

The Google.Flatbuffers.csproj however has target for it:

  <PropertyGroup>
    <TargetFrameworks>netstandard2.0;netstandard2.1;net6.0;net8.0</TargetFrameworks>

Can we have the support for netstandard2.0 documented please?