Adding a more realistic + configurable Bokeh Shader to examples (#3182)
Use Shader Defines for Bokeh Shader 2

- from `THREE.BokehShader.generate(rings, samples);`
- to `material.defines = {RINGS: rings, SAMPLES}`
- thanks to @gyro3 suggestion in #3182
Merge remote-tracking branch 'zz85/bokeh2' into dev