Doc: Explain different usages of "Restrict to MIME types"
Different MIME type restrictions can be specified for auto
formatting and executing the menu command.
Update the screenshot that shows Beautifier options.
Change-Id: Ie6028bef252c6b13d87c6c4eed465eddae991408
Reviewed-by:
Eike Ziller <eike.ziller@qt.io>

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