feat(card): hint to use click as hover fallback on mobile

[lubber-de]

Description

Added a hint how to use a card dimmer on mobile as discussed in https://github.com/fomantic/Fomantic-UI/discussions/2221#discussioncomment-2124079

Screenshot

[lubber-de]

@fomantic/maintainers Please review if you find time. Thx 🙂