I’ve implemented the code according to the following two (Unity) resources.
Dev Diary - Research Report: 2D Sprite Outline Shaders
Writing Shaders In Unity - 2D Sprite Outline - Beginner Tutorial
Well, it was important to me to work with references^^. And since both explained the topic quite well, I decided to start with an inset outline. It seems drawing the outline around the sprite requires a different type of shader. I’ve not yet found a proper resource for that though. This is why I labeled the issue with help-wanted 
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