feat: cleanup and adx support

[xhayper]

• support astrodx's related bg and audio files
• code cleanup (including csproj and use non-deprecated features)
• update dependencies
• ver bump 4.2.1 => 4.3.0
• dotnet framework 4.7.2 => dotnet core 6
• unity 2021.3.16f1c1 => unity 2022.3.15f1