TASK: Add configuration files for RTD

[kdambekalns]

This add .readthedocs.yaml files for the collection (handling Neos.Neos) and for neos.Media, to solve failing documentation rendering.

Review instructions

This can be compared to the configuration we have in place for Neos.Flow in the Flow development collection.

Checklist

• Code follows the PSR-2 coding style
• Tests have been created, run and adjusted as needed
• The PR is created against the lowest maintained branch
• Reviewer - PR Title is brief but complete and starts with FEATURE|TASK|BUGFIX
• Reviewer - The first section explains the change briefly for change-logs
• Reviewer - Breaking Changes are marked with !!! and have upgrade-instructions

[kdambekalns]

Yay, it works for Neos.Neos:

• https://readthedocs.org/projects/neos/builds/22061354/

But not for Neos.Media:

• https://readthedocs.org/projects/neos-media/builds/22061355/