Grid styling options

[ericemc3]

It is aesthetically interesting to differentiate the appearance of certain grid lines:

Note : this is possible with vega-lite: with the properties gridOpacity or gridDash for example, to which one can associate a function.

PS: Plot is a great library, very intellectually stimulating, and the 21 beautifully written articles in the https://observablehq.com/collection/@observablehq/plot collection should be read by all data scientists!

[Fil]

Please copy this comment onto #114 and close the issue.