feat: add scales.grid.step option

[dolsem]

This PR adds an option that allows drawing grid lines every step tick, instead of drawing them on every tick. You can also set it to Number.POSITIVE_INFINITY to only have grid lines around the origin, to make it look a little like a cartesian coordinate system.

I asked about this on DIscord but didn't get any response.

If there is interest, I will add tests for this and finalize the PR.

[LeeLenaleee]

You could achieve the same behaviour with using the scriptable options for the grid color if i understand your use case correct.