Implement ScanlineEffect

[vanruesc]

Description

Implement a ScanlineEffect.

Tasks

• Create ScanlineEffect.
• Create scanline demo.
• Add unit test.

Implementation Details

• The implementation from v6 can be copied mostly as-is.

[balraj-johal]

Hi, I'd like to help out with this ticket if possible. As the implementation can be mostly lifted from V6 this seems like something I can take on :) Also confirming that I have read the contributors guide.

[vanruesc]

Thanks! Feel free to ask if something's unclear.

[balraj-johal]

@vanruesc I've created a PR for this issue, #602 :)