Adding another build command to completely delete and rebuild the Contentful space

[matthias-hausberger]

This PR adds a different build command that can be used to completely delete any entries in the given CTFL space using contentful-clean-space. The build command makes sure that the deletion only happens in the production environment. It will then rebuild everything just like the default build command for the starter.

This is only to be used for QA or Demo environments to completely reset the environment to it's default space. In order to trigger the "complete reset", one can simply click "redeploy" in Vercel.

[vercel[bot]]

@ninetailed-matthias is attempting to deploy a commit to the Ninetailed Team on Vercel.

A member of the Team first needs to authorize it.

[cwkosman]

Approved