Blocks - Add more Effects

[JGames101]

Scratch currently has a few effects - Ghost, Whirl, Colour, Fisheye, Pixelate, Mosaic, and Brightness. Mostly though, only Ghost, Brightness, and maybe colour are useful for most projects. However, because Scratch 3 is being made in HTML5, there are a lot of possibilities to implement more effects. The https://developer.mozilla.org/en-US/docs/Web/API/CanvasRenderingContext2D/filter Canvas Filter supports the same effects and more as the CSS filter, so I see an opportunity to add:
Blur Effect
Invert Colour Effect
Saturation Effect

[thisandagain]

@JGames101 our effects are rendered in WebGL not CSS so these particular implementations are not useful to us, but we'll track this as a feature request. Thanks!

If you are interested in how effects are implemented in Scratch 3.0 I recommend taking a look at the scratch-render repository.