feat. add snapToPoint for line chart and support for supplied xDomain

[cam-shaw]

Purpose
Currently, the cursor moves smoothly along the line which creates a nice user experience but it may not accurately represent the data underneath the cursor at the point in time along x-axis.

By adding this snapToPoint functionality, we are now able to ensure the cursor sticks to the nearest data point on the chart compared to where the cursor/touch-point is. This can be important in finance applications where you don't want to falsely represent a value at a particular point in time.

xDomain purpose
When showing a chart that has partial data for the day (but is still represented on the x-axis with the full scale), we need to ensure the linear scale is performing correctly.

Snap On

e.g.

 <LineChart.CursorCrosshair
  snapToPoint // This is the important prop
  color={'transparent'}
  minDurationMs={150}
  onEnded={onTouchEnd}
  onActivated={onTouchActivated}
/>

Snap.on.mov

Snap off - Default behaviour

Snap.off.-.Default.mov

[arancauchi]

Thanks for the PR :)

If you could perhaps create a short recording of this feature in action, that would be fantastic, we can use that in the README

[cam-shaw]

@arancauchi Have added some recordings to the original comment above!
I have an update coming to this PR later today that greatly improves the code. We actively use this update in prod at the moment.

[cam-shaw]

@arancauchi I have updated this PR with some of our latest code and a bit of a better description.

[arancauchi]

Thanks @cam-shaw i'll take a look.