I couldn’t find one, so I made a MCVE (minimal cljs vscode extension).
It’s a translation of the “Hello World Minimal Sample” for VSCode.
I included steps to utilize live reloading of code, which lets you change your cljs code with shadow-cljs watching, leading to a pretty neat workflow!
If you follow the tutorial to the very end you get to use the REPL as well! I haven’t gotten far there yet, but hopefully this will spell well for debugging efforts made using this approach to create extensions. 
I hope this is useful for someone.
Have a nice day!