Use x/y offset for the DropShadowFilter instead of rotation/distance

[bigtimebuddy]

Closes #256

Changed

• Deprecated rotation and distance from DropShadowFilter in favor of offset.x and offset.y

import { DropShadowFilter } from '@pixi/filters-drop-shadow';

// Set with constructor options
const filter = new DropShadowFilter({
  offset: { x: 2, y: 2 }, // can also be Point
});

// Set with the offset member
filter.offset.set(4, 4);