feat(gx): add incomplete 'CGxDeviceGLSDL' (#2)

* chore(build): add vendored SDL 3.0.0 library

* chore(build): add vendored glew-cmake-2.2.0 library

* feat(console): in the presence of -opengl launch flag, change GxApi to OpenGl

* feat(gx): add uncompleted CGxDeviceGLSDL targeting Windows and Linux

* chore(build): change SDL3 linkage from shared (bad) to to static (good)

vendor/sdl-3.0.0/Xcode/SDL/pkg-support/resources/ReadMe.txt

@@ -0,0 +1,44 @@
+The Simple DirectMedia Layer (SDL for short) is a cross-platform 
+library designed to make it easy to write multi-media software, 
+such as games and emulators.
+
+The Simple DirectMedia Layer library source code is available from: 
+http://www.libsdl.org/
+
+This library is distributed under the terms of the zlib license: 
+http://zlib.net/zlib_license.html
+
+
+This packages contains the SDL framework for macOS. 
+Conforming with Apple guidelines, this framework 
+contains both the SDL runtime component and development header files.
+
+
+To Install:
+Copy the SDL3.framework to /Library/Frameworks
+
+You may alternatively install it in <Your home directory>/Library/Frameworks 
+if your access privileges are not high enough.
+
+
+Use in CMake projects:
+SDL3.framework can be used in CMake projects using the following pattern:
+```
+find_package(SDL3 REQUIRED COMPONENTS SDL3)
+add_executable(my_game ${MY_SOURCES})
+target_link_libraries(my_game PRIVATE SDL3::SDL3)
+```
+If SDL3.framework is installed in a non-standard location,
+please refer to the following link for ways to configure CMake:
+https://cmake.org/cmake/help/latest/command/find_package.html#config-mode-search-procedure
+
+
+Additional References:
+
+ - Screencast tutorials for getting started with OpenSceneGraph/macOS are 
+ 	available at:
+	http://www.openscenegraph.org/projects/osg/wiki/Support/Tutorials/MacOSXTips
+	Though these are OpenSceneGraph centric, the same exact concepts apply to 
+	SDL, thus the videos are recommended for everybody getting started with
+	developing on macOS. (You can skim over the PlugIns stuff since SDL
+	doesn't have any PlugIns to worry about.)