Enhance MSCB docs

[knoobie]

Currently the MSCB docs are quite limited making me searching other repos for solutions.

Technically, I know the MSCB can do "anything" the normal Combobox is capable - but this knowledge is not wide spread.. making things like "How can I change the chips label independed of the dropdown value" incredible hard to find.

Thanks to @TatuLund's comment here vaadin/web-components#6595 (comment) I could find it; but something like this should be in the docs and not hidden in issues.

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[yuriy-fix]

The particular use-case could be documented as an explicit example on MSCB page.
MSCB documentation page is mentioning that it supports all of the same features as regular ComboBox and links to its docs. We could consider making it more noticeable with an admonition.