* Fixing typecast warnings generated by visual studio 2019 in examples.

* Changes to fixes based on feedback

Co-authored-by: Jeffery Myers <JefMyers@blizzard.com>

Without GLFW_OPENGL_FORWARD_COMPAT, running this as a standalone will yield the error:
```
NSGL: The targeted version of macOS only supports forward-compatible core profile contexts for OpenGL 3.2 and above
```

Stumbled on this example and I love this! Adding instructions that work for me on MacOS.. Note that glfw3 will need to be statically built locally and copied to this external/libs directory on mac. I can upload my static version, but it probably makes sense to do this only if there's some general naming convention for adding platform specific folders. Like "external_osx/lib" or "external/lib_osx". Then I'll drop my static libs in there.

See #1304

Still working on the sample but almost finished. Some rlgl internals
redesign required and it will be ready!