docs: add 'Require a community to publish' section in Operate customization

[Samk13]

❤️ Thank you for your contribution!

Description

Closes: #757

Checklist

Ticks in all boxes and 🟢 on all GitHub actions status checks are required to merge:

• I'm aware of the code of conduct.
• I've created logical separate commits and followed the commit message format.
• I've targeted the master branch.
• If this documentation change impacts the current release of InvenioRDM, I will backport it to the production branch following approval or indicate to a maintainer that it should be backported.

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[fenekku]

Thanks for that! Check the suggestions to your liking.

[ntarocco]

Fixed conflicts, thank you for the doc!