Add support for hell packet/dependency manager

[ksanderon]

Hello,

I'v created proxy repository for using GLFW with hell packet/dependency manager as part of action to create ready to use set of most frequently used and valuable C++ open source libraries (I'm main contributor of hell).

However during this task I found that GLFW have great support for cmake(clear options, nice install tree etc, which is unfortunately very uncommon for most of other projects) so proxy repository could be not needed if there could be added to root of GLFW official repository only one small file: .hell.json.

With content similar to:

{
  "=":[],
  "GLFW_BUILD_SHARED_LIBS=OFF":[],
  "GLFW_BUILD_SHARED_LIBS=ON":[],
  "GLFW_USE_CHDIR=OFF":[],
  "GLFW_USE_CHDIR=ON":[],
  "GLFW_USE_HYBRID_HPG=OFF":[],
  "GLFW_USE_HYBRID_HPG=ON":[],
  "GLFW_USE_MENUBAR=OFF":[],
  "GLFW_USE_MENUBAR=ON":[],
  "GLFW_USE_MIR=OFF":[],
  "GLFW_USE_MIR=ON":[],
  "GLFW_USE_MSVC_RUNTIME_LIBRARY_DLL=OFF":[],
  "GLFW_USE_MSVC_RUNTIME_LIBRARY_DLL=ON":[],
  "GLFW_USE_OSMESA=OFF":[],
  "GLFW_USE_OSMESA=ON":[],
  "GLFW_USE_RETINA=OFF":[],
  "GLFW_USE_RETINA=ON":[],
  "GLFW_USE_WAYLAND=OFF":[],
  "GLFW_USE_WAYLAND=ON":[],
  "GLFW_VULKAN_STATIC=OFF":[],
  "GLFW_VULKAN_STATIC=ON":[]
}

It will allow hell tool to detect possible/declared options of GLFW during dependency tree resolving.

In very short words hell is like npm or pip but for C and C++(eventually other languages which cmake support), do not have central packets repository and works based on git tags + cmake - so build everything from sources instead using precompiled binaries.

More details about hell:

• Short description of Hell
• Hell FAQ
• Online search engine for projects with hell support

So finally question :)

Is there possibility to accept this kind of PR? I hope from your perspective it's very minor change, but from mine it will be something really awesome as GLFW can be first widely known project with native support for hell - because of that how nice GLFW build system is maintained ;)