Migrate the project to properly use go module versioning

[ysmood]

The project is using v2 tag on git repo, but it doesn't follow the rule of standard go module.

FYI: https://go.dev/blog/v2-go-modules

If you try to run directly it will fail:

go run github.com/ViRb3/wgcf@latest 

After this fix, you will be able to run the wgcf cli without having to install it:

go run github.com/ViRb3/wgcf/v2@latest -h
go run github.com/ViRb3/wgcf/v2@latest register
go run github.com/ViRb3/wgcf/v2@latest generate