Add FreeImage about vcpkg HOT 1 CLOSED

I looked a bit into this (it is a required dep for #14).
Apparently freeimage ships a lot of its dependencies as part of their repo. To use the version of this libraries provided by vcpkg, the best strategy is probably to roll our own CMake-based build system, as done for zziplib and fastlz.

Required dependencies (ticked if they are already present in vcpkg):

• zlib
• libjpeg (provided by the header-compatible libjpeg-turbo)
• libpng
• tiff
• openexr https://github.com/openexr/openexr
• openjpg https://github.com/uclouvain/openjpeg
• libjxr https://jxrlib.codeplex.com/ (not sure if this is the official upstream repository)
• libwebp https://github.com/webmproject/libwebp
• libraw http://www.libraw.org/

Related links :

• https://sourceforge.net/p/freeimage/bugs/232/
• https://anonscm.debian.org/cgit/debian-science/packages/freeimage.git/tree/debian

from vcpkg.