Create a Repeatable CONTRIBUTING guide

[yordis]

I am trying to contribute to the package, but I haven't been able to follow the https://github.com/crossplane-contrib/provider-digitalocean/blob/main/docs/CONTRIBUTING.md

Ideally, the contributing guide has a repeatable how-to guide that people could follow and be able to contribute to the project.

[jbw976]

thanks for sharing your experience @yordis!! looks like you can run make submodules to get the build submodule cloned first, and then make will have what it needs to start running.

Agreed on updating the contributing guide to have repeatable steps for new contributors 🤓