Imagecodecs

- Add Zopfli codec.
- Add Snappy codec.
- Rename j2k codec to jpeg2k.
- Rename jxr codec to jpegxr.
- Use Debian's jxrlib.
- Support pathlib and binary streams in imread and imwrite.
- Move external C declarations to pxd files.
- Move shared code to pxi file.
- Update copyright notices.

- Add version functions.
- Add Brotli codec.
- Add optional JPEG XL codec via Brunsli repacker.

- Sync with imagecodecs-lite.

- Add AEC codec via libaec.
- Do not require scikit-image for testing.
- Require CharLS 2.1.

- Add bitshuffle codec.
- Fix formatting of unknown error numbers.
- Fix test failures with official python-lzf.

- Rebuild with updated dependencies.