Update to .net 8

[fpellet]

Description

Add .net 8 and upgrade dependencies. Add upgrade dependencies of #566

How to test

Building the solution, running tests, and running the sample endpoint app

Related issues

Close #570 Close #565

[64J0]

Just a first heads-up, can you please target the develop branch instead of master? The contributing workflow is documented here: https://github.com/giraffe-fsharp/Giraffe?tab=readme-ov-file#contributing.

[fpellet]

@64J0 done. Sorry for the delay, I forgot to do it 😅