Feature Request: Add `markevery` as a param to mpf.plot()

[varunskao]

The request is to add in a feature for markevery such that the plot can mark specific points in the plot, where the size, color and shape can be configured, or when not provided, defaults to a set value. A reference to what has been implemented in matplotlib is provided below:

https://matplotlib.org/stable/gallery/lines_bars_and_markers/markevery_demo.html

Happy to help with the implementation.

[DanielGoldfarb]

@kata1st It seems to me that a markevery specification must be associated with a specific line.

So I guess it would apply only to mpf.plot(df,type='line') or to individual mpf.make_addplot() calls where type is unspecified (defaults to 'line') or where type='line'. Is this what you had in mind?

Can you please provide a use case for when you would want to do this? Thank you. --Daniel