Document Manage Communities page

[zubeydecivelek]

https://github.com/CERNDocumentServer/docs-cds-rdm/blob/main/docs/communities/manage.md

Add documentation that explains:

• Settings: What can be configured (e.g. name, description, visibility).
• Members: How to add/remove members and manage roles (e.g. owner, curator, manager, reader).
• Browse & collections
• Submissions: requests & reviews: How submission requests and the review workflow work from the community side.
• Curation: What curation means in this context and what curators can do.