v5.15.0

What's Changed

• Update README.md badges for CI and coverage in #54
• Fix path for NuGet artifacts in #55
• Use Powershell as the shell for NuGet uploads in #56
• Update build.yml to ubuntu-24.04 in #57
• Fix nullability warnings in #58
• Enable Trusted Publishing on nuget.org in #59
• Bump MailKit and MimeKit to v4.16.0 by @dependabot[bot] in #60, resolving security issues
• Bump version v5.15 in #61

Full Changelog: v5.14.0...v5.15.0