Background grid

[terjew]

It would be really useful if there was an option to draw a background grid with the same lines as the tickmarks in the X/Y axis. The grid should ideally be a bit more dampened than the grid lines, eg by using thinner and/or dashed lines.

[huww98]

This can be implemented as a plugin, just like the built-in d3Axis plugin.

Contributions are welcome.