TASK: Document that scatter does NOT move fallbacks!

[mhsdesign]

Followup to using scatter now: neos/neos-ui#3876

GOTO a page ("Multiple columns") in EN_US, which only has fallbacks and no content variants.
Move an element in EN_US with the new scatter content behaviour ("Why, Mary Ann..." below "Hand it over here...")
The element is only moved in EN_US and NOT moved in EN_UK.

In Neos 8.3 they were moved, as long it was just a fallback:

If you previously changed the text in 8.3 (create a variant in EN_UK) the move in US is not affected in UK.

Neos 9.0 makes that behaviour more consistent. In case the variants should also be moved gatherSpecializations should be configured:

'Neos.Neos:Content':
  options:
    moveNodeStrategy: gatherSpecializations

there is no exact behaviour like Neos 8.3 in the core.

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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