Update to .net8

[stefannikolei]

I saw that this project is still on .net6.

So i updated it to net8 :)

[JimBobSquarePants]

Thanks for this. We'll need to shift to a new major v3 version to allow the changes.

The version should be forced for nightlies in a manner similar to the following.
https://github.com/SixLabors/ImageSharp/blob/08432174cf85a3d26180c0aa2b607b9c6ff2e695/src/ImageSharp/ImageSharp.csproj#L25-L28

I've already created a branch to house the V2 version.

[JimBobSquarePants]

Actually, you need to update the DotNet Setup and Preview tasks. I think there's some nuance there so I'd compare it with ImageSharp's one.

[stefannikolei]

It seems to me that this repo is configured in another way than ImageSharp. The Build seems to only run when you approve the changes

[JimBobSquarePants]

Closed in favor of #463 Sorry!