I have placed the mod into the mods folder of my development environment. Attempting to launch the game results in a java.lang.NoSuchMethodError: net.minecraft.client.Minecraft.func_71410_x()Lnet/minecraft/client/Minecraft. Apparently the issue is on line 50: where the Minecraft instance is obtained.

As such I believe this could possibly be an issue with new Forge mappings: at the moment they are 20210309-1.16.5 for me. My Forge is currently at 1.16.5-36.0.48.

I have attached the crash report below.

crash-2021-03-10_21.29.53-fml.txt

Thanks for the report!
I have created a version updated to be built against the latest Forge.
I think it should work, please let me know if you run into any issues with it.