[JS] Intl.Collator collation constructor option

[chrisdavidmills]

Acceptance criteria

1. • The listed features are documented sufficiently on MDN
2. • BCD is updated
3. • Interactive example and data repos are updated if appropriate
4. • The content has been reviewed as needed

Features to document

1. Intl.Collator collation constructor option. Not yet documented on Collator() constructor page, will need adding, perhaps with an example, and updated BCD?

Related Gecko bugs

1. • Add support for a "collation" property to the options-bag passed to Intl.Collator

For folks helping with Firefox-related documentation features — make sure above AC have been done, but also:

• Set bugs to dev-doc-complete
• Add entry to Firefox release notes if feature is enabled in release
• Add entry to Firefox experimental features page if feature is not yet enabled in release

[hamishwillee]

There is a good description of what this change means in tc39/ecma402#380

• BCD: Add Intl.Collator option for collation browser-compat-data#8471
• Interactive example: Add options example to intl-collator interactive-examples#1748 - NOTE this is not of collation, but is showing an "option".
• Docs and release note update: Intl.Collator options now take collation option (FF85) #788
• Note to inform Dev team: https://bugzilla.mozilla.org/show_bug.cgi?id=1670062#c5

FYI some other minor fixes to docs in there to0 - e.g. caseFirst option was not documented.

@chrisdavidmills Ready for review at your convenience.

[chrisdavidmills]

OK, set to dev-doc-complete, and closing!