[Outlook] (shared mailboxes) Document scenarios for add-in availability in shared mailboxes (#5098)

* Draft shared mailbox scenarios

* Add default add-in scenario

* Apply feedback from review

* Apply suggestion from review

* Apply suggestions from review

* Clarify default add-in support in Outlook on Mac

* Fix typo

* Clarify wording

* Add suggestion from review

* Apply suggestion from review

* Clarify shared mailbox behavior in new Outlook on Windows

* Fix table heading

* Fix format

* Update table order and clarify getSharedPropertiesAsync support

* Fix typo

Co-authored-by: Copilot <[email protected]>

* Update ms.date

* Apply suggestions from review

Co-authored-by: Elizabeth Samuel <[email protected]>

* Apply suggestion from review

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Co-authored-by: Copilot <[email protected]>
Co-authored-by: Elizabeth Samuel <[email protected]>

Author: 3 people