Support on the Compatibility renderer

[TomCrowBG]

The Rendering API used for Compatibility Mode is not able to compile the shaders used in this plugin.

drivers/gles3/shader_gles3.cpp:254 - ParticlesShaderGLES3: Vertex shader compilation failed:
  0(498) : error C1059: non constant expression in initialization
  
  drivers/gles3/shader_gles3.cpp:348 - Method/function failed.
  ./drivers/gles3/shader_gles3.h:222 - shader failed to compile, unable to bind shader.

[celyk]

Last I checked GPUParticles and compute shaders don't work in the OpenGL backend, so this was just not in scope. I'll leave the issue open in case a workaround is found.

[bitdream]

Regarding this issue, I've just made a pull request. It not only failed in compability mode, but also in mobile mode(devices).
Please check:
#9

[celyk]

Turns out GPUParticles does work on compatibility now. I hope to support it moving forward