Missing changelog for 0.17.16

[yisibl]

https://github.com/image-rs/image-png/releases/tag/v0.17.16

[svgeesus]

I had seen the latest posted changelog (for 1.17.15) which mentioned cLLi and mDCv, and came here to report the spelling change on these chunks, but it is already fixed.

[fintelia]

Fixed in #570, and noted that cLLI and mDCV were actually renamed before the release so all versions should either completely ignore those chunks or only look for them under their new names