[Documentation][HxAccordion] Clarify documentation

[jolaquai]

https://havit.blazor.eu/components/HxAccordion#HxAccordion-api

ID of the single expanded item (if StayOpen is true, use ExpandedItemIds, several items can be expanded). Do not use a constant value as it reverts the accordion to that item on every roundtrip. Use InitialExpandedItemId to set the initial state.

I mean, yes, obviously, the docs state that the consumer should use the parameter for multiple IDs, but it's not clear that this is a requirement; I wouldn't immediately consider that to mean "the other EventCallback won't even be invoked when StayOpen is true".
Perhaps this could be clarified in the docs, maybe in other places where a StayOpen equivalent could cause similar confusion?