Implement GlitchEffect

[vanruesc]

Description

Implement a GlitchEffect.

Tasks

• Create GlitchEffect.
• Create glitch demo. Also use ChromaticAberrationEffect in that demo.
• Add unit test.

Implementation Details

• Should be done after ChromaticAberrationEffect has been implemented.
• The implementation from v6 can be copied mostly as-is.
• The effect should define an offset output uniform for chromatic aberration.
  • Also provide an offset getter for this uniform's value.
  • The ChromaticAberrationEffect will automatically use the offset uniform as input if it runs after a GlitchEffect.