Graphic mode add access to buffered data

[TravisThomp]

Adding direct access to the buffer to allow for easy manipulation. Convenient for applying filters.

[IniterWorker]

1. From a graphics mode standpoint, I don't think exposing an "unchecked" method without the business logic of the buffering mechanism is a good idea. If you update something directly, the draw window will not reflect those changes.

2. If you need raw performance, you can use the unbuffered mode.

let mut display_driver = Gc9a01::new(
    interface,
    DisplayResolution240x240,
    DisplayRotation::Rotate180,
);

3. I think the filter should be a top layer of embedded-graphics, if you want it to be portable.

Let me know if you have more feedback about it.

[TravisThomp]

Thanks, that makes more sense, especially for portability. I solved my issue by using embedded-graphics-framebuf and the driver in unbuffered mode.

As for future considerations, would it be worth adding a get_pixel_at(x, y) method? It would resolve your concern about the unchecked method, but also provide some access to the data stored in the buffer.