Add support for embedded bitmap graphs

[tiby312]

No description provided.

[tiby312]

I think the api should be the user gets to pick a resolution, and then they can literally add individual pixels. This plot would then be scaled to fit into the plotting area and could be overlayed on top of other svg plots.

let data=[0u8;64*64];
let bitmap=poloto::plot("foo").bitmap().with_resolution([64,64]).buffered(data).

[tiby312]

unlike other iterators, this one should probably allowing passing of x,y and color. not just x and y.

[tiby312]

on second thought the above api doesnt allow the user to be able render specific pixels. maybe this:

let bitmap=poloto::plot("foo").bitmap().map(|pixel|map_pixel_to_actual_value(pixel)).buffered(pixel_data)