Option for grid lines

[morphy2k]

Great library, thank you for your work!
As far as I have seen, there is no way to display grid lines. I would very much appreciate an option for that.

[tiby312]

Good idea we can extend the code related to creating the dash lines

[tiby312]

I added a way to add lines on the ticks with xtick_lines and ytick_lines. I would still like to explore how to let user do grid lines between the ticks.

[morphy2k]

Awesome, thank you!
I think having the option to render the lines only when needed would be a good thing. As you described.