Function: add_stroke_effect

--Usage--
> add_stroke_effect(input: image, radius: number, blur: number, color: color)

Add a stroke effect around an image.

--Parameters--
! Parameter				Type				Description
| @input@				[[type:image]]		Image that needs a stroke effect
| @radius@		[[type:int]]		Size of the stroke, in pixels
| @blur@		[[type:int]]		Size of the blur of the stroke, in pixels. Optional, defaults to 0
| @color@	[[type:color]]		Color of the stroke
| @include_image@	[[type:boolean]]		Draw the original image in the middle of the stroke effect. Optional, defaults to true