message: update instruction to build on macos
diff: @@ -56,6 +56,13 @@ Cesium for Unreal depends on Cesium's high-precision geospatial C++ library - [C
  cmake --build build --config Debug --target install # Optional, recommended for debugging
  ```
  + * CMake configuration and build on MacOS platform:
  +
  + ```cmd
  + cmake -B build -S . -DCMAKE_BUILD_TYPE=Release # Can optionally compile with RelWithDebInfo or MinSizeRel.
  + cmake --build build --target install
  + ```
  +
  * CMake configuration and build on Linux platform:
  ```cmd
  