Update to .NET 6? #52

Looks like TryFSharp uses some older version of F# (noticed by certain new .NET 6.0 methods not being available). Not sure what version, since the following snippet fails to run:

printfn "%A" System.Environment.Version  // throws error: FABLE: Cannot resolve System.Environment.get_Version

It should be noted that the context-sensitive help just works, it recognizes Environment.Version just fine and shows its members.

PS, System.Runtime.InteropServices.RuntimeInformation.FrameworkDescription doesn't work either, since the Interop dll isn't available (afaict).