Support double click recognition in `bevy_picking`.

[443eb9]

What problem does this solve or what need does it fill?

bevy_picking currently only able to recognize the type of clicks, but can't, for counts.

What solution would you like?

Add a DoubleClick type.

What alternative(s) have you considered?

Supporting MultipleClick<const N: usize> would be better.

Additional context

None