Support Rgb565 and Bgr565

[windoze]

Some module, namely M5Stick-C, has pixel color set to BGR565 instead of RGB565. With pixel color in generic parameter, user may need to specify color when creating the instance, i.e.

let mut display = st7789::ST7789::<_, _, Bgr565>::new(...);

[almindor]

Thanks, would you consider expanding https://github.com/almindor/mipidsi instead tho? I've sort of deprecated this driver for it as it provides a generic setup with 90% of the code base shared accross all MIPI-DSI drivers. You can expand the ST7789 there easily and test.

[almindor]

Needs cargo fmt

[windoze]

Sure, I'll take a look