Add .NET 10 target framework and update dependencies

[thekim1]

Summary

Adds net10.0 as a supported target framework and updates the Microsoft.Extensions.* dependencies to the 10.0 release line, following the package's versioning policy that the major version tracks the major version of its Microsoft.Extensions.Logging dependency.

All existing, in-support target frameworks (netstandard2.0, net8.0, net9.0, and net48 for tests) are retained.

Changes

• Library (src/Seq.Extensions.Logging)
  • TargetFrameworks: added net10.0 → netstandard2.0;net8.0;net9.0;net10.0
  • Updated Microsoft.Extensions.Logging, .DependencyInjection, and .Logging.Configuration to 10.0.9
• Tests (test/Seq.Extensions.Logging.Tests)
  • TargetFrameworks: added net10.0 → net48;net8.0;net9.0;net10.0
  • Updated Microsoft.NET.Test.Sdk, Microsoft.TestPlatform.ObjectModel, xunit, and xunit.runner.visualstudio to current releases
• Examples
  • ConsoleExample and WebExample retargamplepackage references updated to10.0.9`
• Build / CI
  • global.json SDK pin updated from 9.0.ard: latestFeature)
  • ci.yml setup-dotnet now installs `8.o every test TFM has its matching runtime
• Versioning
  • VersionPrefix bumped from 9.0.1 to 10.0.0
• README
  • Getting-started note updated to reflect .NET 8.0+
  • Versioning policy rewritten to describe the 10.* release line and continued coverage of net8.0/net9.0

Verification

• Library builds cleanly (0 warnings, 0 errors) for all four TFMs: netstandard2.0, net8.0, net9.0, net10.0
• Tests pass: 92/92 on net10.0, net9.0, net8.0, and net48
• Example projects build and run on `net10.0

Notes

• No source-code changes were done
• No breaking changes for consumers on older runtimes; existing TFMs and the public API are unchanged.

[KodrAus]

Thanks @thekim1!