Document supported target frameworks for testing platform

[nohwnd]

MTP is often mentioned to not support .net framework, add short note about being supported.

stryker-mutator/stryker-net#3094 (comment)

Summary

Describe your changes here.

Fixes #Issue_Number (if available)

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Internal previews

📄 File	🔗 Preview link
docs/core/testing/microsoft-testing-platform-intro.md	Microsoft.Testing.Platform overview

[Copilot]

Pull request overview

Adds a short documentation note clarifying that Microsoft.Testing.Platform (MTP) supports .NET Framework, addressing recurring confusion about framework support.

Changes:

• Added a new Supported target frameworks section to the MTP overview article.
• Documented support for .NET 8+, .NET Framework 4.6.2+, and referenced .NET Standard 2.0 targeting for compatibility.

[Copilot]

This sentence is a bit inconsistent/unclear about what’s supported. Elsewhere the docs state "The minimum supported .NET version is .NET 8" (see docs/core/testing/microsoft-testing-platform-migration-from-v1-to-v2.md:19), so consider changing ".NET (.NET 8 SDK and later)" to ".NET 8 and later" to avoid implying the SDK is required at runtime. Also use the standard product name ".NET Standard 2.0" (not "NETStandard 2.0") and consider rephrasing the last clause to describe API compatibility across .NET implementations/target frameworks rather than "other runtimes".

Suggested change

	Microsoft.Testing.Platform supports .NET (.NET 8 SDK and later), .NET Framework (versions 4.6.2 and later), and targets NETStandard 2.0 for maximum compatiblity with other runtimes.
	Microsoft.Testing.Platform targets .NET 8 and later, .NET Framework 4.6.2 and later, and .NET Standard 2.0 for maximum API compatibility across .NET implementations and target frameworks.