- compile against LWJGL 3.2.3 version
- restrict to the Vulkan demos (code & resources)
- add Gradle wrapper & build script
- use GraalVM native-image utility to produce native executable
  containing the Vulkan demos.

- compile against LWJGL 3.2.3 version
- restrict to the OpenGL demos (code & resources)
- exclude the SWT demos for now
- use GraalVM native-image utility to produce native executable
  containing the OpenGL demos.

- src/org/lwjgl/demo/opengl/swt classes are now included in the build
- SWT has different APIs for different platforms, especially in the
  native-to-Java callbacks, which makes it challenging to create
  portable build script to generate platform-specific native images
  from platform-specific configuration files
- Gluon provides the client-gradle-plugin/client-maven-plugin for
  Gradle/Maven, which have excellent supports for platform-specific
  configuration files to generate platform-specific native images
- platform-specific configuration files for SWT are in the
  res/META-INF/substrate/config directory which are used by the Gluon
  plugins during the native-image building.