add CrossPlatformProcessLock - #4

Process completed with exit code 2.

This call site is reachable on all platforms. 'FileStream.Lock(long, long)' is unsupported on: 'macOS/OSX'.

This call site is reachable on all platforms. 'FileStream.Unlock(long, long)' is unsupported on: 'macOS/OSX'.

This call site is reachable on all platforms. 'FileStream.Lock(long, long)' is unsupported on: 'macOS/OSX'. (https://learn.microsoft.com/dotnet/fundamentals/code-analysis/quality-rules/ca1416)

This call site is reachable on all platforms. 'FileStream.Unlock(long, long)' is unsupported on: 'macOS/OSX'. (https://learn.microsoft.com/dotnet/fundamentals/code-analysis/quality-rules/ca1416)

This call site is reachable on all platforms. 'FileStream.Lock(long, long)' is unsupported on: 'macOS/OSX'. (https://learn.microsoft.com/dotnet/fundamentals/code-analysis/quality-rules/ca1416)