message: docs: add a note in the readme about using the CMake imported target
diff: @@ -69,6 +69,18 @@ to the files you want to process JSON and set the necessary switches to enable C
  You can further use file [`include/nlohmann/json_fwd.hpp`](https://github.com/nlohmann/json/blob/develop/include/nlohmann/json_fwd.hpp) for forward-declarations. The installation of json_fwd.hpp (as part of cmake's install step), can be achieved by setting `-DJSON_MultipleHeaders=ON`.
  +If this library was built with CMake then you can consume it from another CMake project by using the namespaced imported target from the generated package configuration:
  +```cmake
  +# CMakeLists.txt
  +find_package(nlohmann_json REQUIRED)
  +...
  +add_library(foo ...)
  +...
  +target_link_libraries(foo PRIVATE nlohmann_json::nlohmann_json)
  +```
  +The package configuration file, `nlohmann_jsonConfig.cmake`, can be used either from an install tree or directly out of the build tree.
  +
  +
  ### Package Managers
  :beer: If you are using OS X and [Homebrew](http://brew.sh), just type `brew tap nlohmann/json` and `brew install nlohmann_json` and you're set. If you want the bleeding edge rather than the latest release, use `brew install nlohmann_json --HEAD`.
  