(Webgl2 / WebGPU support) A better outline shader than the one that already exists on the C3 addon stack exchange.
I wrote a short blog post about that a while ago:
construct.net/en/blogs/skymen-13/write-effects-construct-1538
It's a little outdated since now the SDK has changed a lot, including WebGPU and WebGL2 shaders, but still I'd say it's a good starting point.
I would also use c3IDE2 to set up a new dev environment for making shaders
github.com/ConstructFund/c3ide2-cli
Feel free to join the Construct Community Discord server if you have any questions and other addon devs can answer any questions you might have.