Bug fix: reload GL buffers after a resize
Bug fix: reload GL buffers after a resize

* With the test code, I load the GL buffers every 100 frames. They also
  need to be loaded after a GL resize, because the GL context has been
  recreated.

redblobgames/helloworld-sdl2-opengl-emscripten,redblobgames/helloworld-sdl2-opengl-emscripten,redblobgames/helloworld-sdl2-opengl-emscripten