I think you should release the shadow_mod separate from the other mods in the game. Is more preferable downloading the mod than downloading a full game to try out a mod. I checked the code and I doubt your mod has bugs apart from those found in the default game, in other words your mod should be bug free. I checked your code and saw there is no crafting recipe for the block, I wonder if this is intentional.
Also, would you like to contribute to the
Community Collaboration Project? There you don't need to know a lot of coding, all it takes is a node, which is what you have done. :)