Mark a function as an Ecsact codegen plugin entry point. Two C functions
will be created for you that are required for an Ecsact plugin. One will
contain the function you marked as the entry point and be given a “context”
object of type ecsact::CodegenPluginContext.
Mark a function as an Ecsact system implementation. A C function will be
created for you that will call the marked function with safe context struct
from the Ecsact code generator.