Features:
- Add compression of pre-compressed frame data, via `Encoder::write_lzw_pre_encoded_frame`.
- The `color_quant` dependency is now optional. Turning it off disables some
  interfaces that would internally build quantization tables. The generic
  implementation of creating such tables can be prohibitively costly compared
  to specialized algorithms in some use cases.

Optimization:
- Avoid some allocations in by replacing `flat_map` argument with arrays

sha256sum: 80792593675e051cf94a4b111980da2ba60d4a83e43e0048c5693baab3977045  target/package/gif-0.12.0.crate