Implement GlitchEffect

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.

Start by reviewing the v6 implementation and the existing ChromaticAberrationEffect, since the issue says this work depends on it. Create the GlitchEffect, a glitch demo using ChromaticAberrationEffect, and a unit test; it is done when the offset output uniform and getter are provided and all three tasks are complete.