UTF-8 path not supported on Windows

[WinstonMao]

Summary

Hello,
When I dragged a file with the UTF-8 characters into the SDL window, it returned a wrong path.
It seems to only return the wrong path under Windows, and it works fine under Mac OS.

Steps to reproduce

• Platform: Windows 10 Enterprise LTSC 1809
• Framework Version: .NET6
• API: Silk.NET.Windowing
• API Version: 2.18

1. Drop the File named with UTF-8 characters to the SDL window. It returns a wrong path.

2. Inspired by SDL2-CS, I modified the source code of "SdlWindow.cs" and got the following result:
   

3. And here is the file named with UTF-8 characters：
   测试.txt

[Perksey]

Good spot, we’d welcome PRs here.

[Perksey]

Closed by #1810 🎉