3.0.0 Release Candidate

Other than documentation and release note changes, I'm not planning anything else unless I receive more feedback about issues.

https://www.nuget.org/packages/McMaster.Extensions.CommandLineUtils/3.0.0-rc.289
https://www.nuget.org/packages/McMaster.Extensions.Hosting.CommandLine/3.0.0-rc.289

Changes:

• 7281ee9 Prepare 3.0 RC release
• f3a4725 fix: suppress PlatformNotSupportedException on Xamarin of macOS
• 294a829 Minor cleanup and update release notes
• accdd6c feature: support using builder API with generic host (#351)
• cf7506c Merge branch 'release/2.x'
• 2eb7bfa fixup: cleanup obsolete messages for throwOnUnexpectedArg

This list of changes was auto generated.