add dragThreshold prop to A11y component

[claytercek]

Adds an optional dragThreshold prop to the A11y component. If the onClick event delta is greater than this value, the action event handler doesn't fire.

I've run into an issue using this library in combination with the drei MapControls, where drags that start and end on the same A11y target trigger a click event when the user's intention is to just pan the camera.

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[AlaricBaraou]

Hello @claytercek ,
I've never seen this .delta property on click event, can you share where it's coming from ?
Otherwise I'm fine with the logic of this PR

[claytercek]

@AlaricBaraou yeah it's one of the threejs properties that r3f adds to pointer events

https://github.com/pmndrs/react-three-fiber/blob/7dbf70b1f6f91d772958d57548e6dfec5c963ce6/packages/fiber/src/core/events.ts#L24

https://docs.pmnd.rs/react-three-fiber/api/events#event-data