Doesn't work with .NET 9

[gordon-matt]

I noticed the NuGet package for this does not work on .NET 9. It fails with an error in the browser as follows:

The screenshot above is from the WebApplication demo project in this repo.. but the same thing was originally happening on a CMS project of mine where I am using this file manager.

I did try updating the PeachPie version to the latest as well, but that had other issues; a compile time error as follows:
Conversion from "PhpValue" to "ReadOnlySpan" not implemented

@jakubmisek Hoping you can help solve this one?