v0.9.0-rc3

BINDINGS/C++: Added reverse_bytes()
COMMON: Added ZIP compression
COMMON: Added bytes reverse functions
COMMON: Fix order of case:
DOC: Add vcpkg note without CMake
DOC: Added PSD
DOC: Note on unsupported blend operations
EXAMPLES: Show source image compression in probe()
LIBSAIL: Update comments
LIBSAIL: Update flag docs
PNG: Added error message in blend function
PNG: Added note on transparent background
PNG: Apply disposal method only for images with bpp >= 8 (workaround)
PNG: Blend grayscale images
PNG: Store number of frames and plays
PSD: Added PSD codec
SAIL: Apply fix from https://github.com/jtojnar/cmake-snips#concatenating-paths-when-building-pkg-config-files
SAIL: Rename pkg-config variables to have SAIL_ naming
SAIL: Require CMake 3.12 to link against object libraries
SAIL: Update SAIL_COMBINE_CODECS docs
TESTS: Added more ull suffixes
TESTS: Remove unused include string.h
TIFF: Fix empty list of compressions in VCPKG mode