Include chain-spec-generator binaries in release artefacts

[Moliholy]

Currently developers have to include manual steps in their development workflow to build the chain-spec-generator binary in order to be able to get the binary and use it in different workflows (for instance: Zombienet).

If the CI, whenever there is a new release, could build that binary in both platforms (linux and macOS) it'd be really helpful and save a lot of time and improve overall efficiency. Furthermore, other tooling (like POP, for instance) could directly download the binary depending on the platform and further improve development experience.