Regenerate documentation

[nlewo]

We also now use https://github.com/hashicorp/terraform-plugin-docs as suggested by the Terraform documentation.

[nlewo]

It's actually not possible to render the whole documentation. So, this PR is quite mininal:

• all schemas have been generated
• the existing index file have been adapted.

Do you think it is sufficient for a release?

[tiramiseb]

yes