Scene: Allow for customising what button can be used for clicking and dragging, allow for providing custom Sense

[mitchmindtree]

Currently, the Scene allocates a response with Sense::click_and_drag and checks response.dragged() to determine whether the scene should be panned by response.drag_delta(). This is great for users who are happy to have the scene dragged with any button.

However, this is unsuitable for those who wish to only drag with a particular button (e.g. Middle) or to have no drag behaviour at all (e.g. maybe they only want to pan the scene via scrolling).

Potential Solution

• Allow for specifying a custom Sense for the scene. This would allow users to disable the Sense::click_and_drag behaviour if they wish in favour of Sense::hover.
• Allow for optionally specifying a .drag_pointer_button(PointerButton) to enable dragging only with a specific pointer button.

Ideally, we could just add the custom sense method, and then allow the user to check for whatever interaction they would like to pan the scene themselves, though I'm not sure how we'd expose the ability to pan the scene smoothly from inside the user content function 🤔