Print usage information for vcpkg

[mrexodia]

Currently you can find packages on https://vcpkg.io, but there is no usage information on the website.

The following command works:

vcpkg x-package-info --x-json --x-installed glfw3:x64-windows

{
  "results": {
    "glfw3:x64-windows": {
      "version-string": "3.3.4",
      "port-version": 0,
      "triplet": "x64-windows",
      "abi": "fe01dfbeb9b872d7b6d1927f68aded832c717f0e",
      "usage": "The package glfw3:x64-windows provides CMake targets:\n\n    find_package(glfw3 CONFIG REQUIRED)\n    target_link_libraries(main PRIVATE glfw)\n\n",
      "owns": [
        "x64-windows/",
        "x64-windows/bin/",
        "x64-windows/bin/glfw3.dll",
        "x64-windows/bin/glfw3.pdb",
        "x64-windows/debug/",
        "x64-windows/debug/bin/",
        "x64-windows/debug/bin/glfw3.dll",
        "x64-windows/debug/bin/glfw3.pdb",
        "x64-windows/debug/lib/",
        "x64-windows/debug/lib/glfw3dll.lib",
        "x64-windows/debug/lib/pkgconfig/",
        "x64-windows/debug/lib/pkgconfig/glfw3.pc",
        "x64-windows/include/",
        "x64-windows/include/GLFW/",
        "x64-windows/include/GLFW/glfw3.h",
        "x64-windows/include/GLFW/glfw3native.h",
        "x64-windows/lib/",
        "x64-windows/lib/glfw3dll.lib",
        "x64-windows/lib/pkgconfig/",
        "x64-windows/lib/pkgconfig/glfw3.pc",
        "x64-windows/share/",
        "x64-windows/share/glfw3/",
        "x64-windows/share/glfw3/copyright",
        "x64-windows/share/glfw3/glfw3Config.cmake",
        "x64-windows/share/glfw3/glfw3ConfigVersion.cmake",
        "x64-windows/share/glfw3/glfw3Targets-debug.cmake",
        "x64-windows/share/glfw3/glfw3Targets-release.cmake",
        "x64-windows/share/glfw3/glfw3Targets.cmake",
        "x64-windows/share/glfw3/vcpkg_abi_info.txt"
      ]
    }
  }
}

Reference: microsoft/vcpkg-tool#82 (comment)