How to add an Inner Glow to a Tilemap?

Hi guys! I'm working on a shader for a tilemap and want to make an inner glow effect for it. I've looked around for some ways of doing this, but I haven't found anything helpful. I'm using the Shader Graph and Unity 2019.3.13f1. How would I go about doing this?

This image above is a similar effect. The blue lines represent the tiles.

 

https://github.com/Unity-Technologies/2d-gamedemo-robodash
Robodash demo does something kind of like. Can't remember if they use a shader to achieve it. I think they draw another layer instead.