Add an FXAA implementation.
FXAA is an antialiasing technique that is applied in a post-processing pass. This implementation:
- Is a single-pass fragment shader.
- Detects edges.
- Searches for edge endpoints.
- Interpolates colors along the edge to give a smooth, antialiased color gradient.
- Detects and corrects sub-pixel antialiasing.
Related to paraview/paraview#16882 (closed)