message: Adds more documentation for displacement filter.
diff: @@ -11,6 +11,12 @@ import fragment from './displacement.frag';
  * Currently the `r` property of the texture is used to offset the `x`
  * and the `g` property of the texture is used to offset the `y`.
  *
  + * The way it works is it uses the values of the displacement map to look up the
  + * correct pixels to output. This means it's not technically moving the original.
  + * Instead, it's starting at the output and asking "which pixel from the original goes here".
  + * For example, if a displacement map pixel has `red = 1` and the filter scale is `20`,
  + * this filter will output the pixel approximately 20 pixels to the right of the original.
  + *
  * @class
  * @extends PIXI.Filter
  * @memberof PIXI.filters
  