Simplify target frameworks to netstandard2.0 + net8.0

[Jericho]

As discussed here: Jericho/StrongGrid#558, the fact that we do not target netstandard2.0 can cause warnings and assembly conflict/confusion if a developer tries to reference this library from a project targeting netstandard2.0

[Jericho]

🎉 This issue has been resolved in version 0.107.0 🎉

The release is available on:

• GitHub Release
• NuGet Package

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