Replace simple threshold-based grayscale quantization with ordered
dithering using a 4x4 Bayer matrix. This eliminates color banding
artifacts and produces smoother gradients on e-ink display.
- Add 4x4 Bayer dithering matrix for 16-level threshold patterns
- Modify grayscaleTo2Bit() to use pixel position for dithering
- Simulates smooth grayscale transitions in BW mode without flicker
## Summary
- Add basic JPG image support
- Map JPG back to 2-bit BMP output
- Can be used to later render the BMP file from disk or directly pass to
output if wanted
- Give the 3 passes over the data needed to render grayscale content,
putting it on disk is preferred to outputting it multiple times
## Additional Context
- WIP, looking forward to BMP support from
https://github.com/daveallie/crosspoint-reader/pull/16
- Addresses some of #11
