message: Clarify how construction works
diff: @@ -68,7 +68,7 @@ Here
  * two components will be defined as fields on the reactor struct, the fields being named `component_a` and `component_b` respectively,
  * their type will be `crate::components::comp_a::CompA` (automatically deduced from the name),
  -* they will be constructed passing in `constructor_arg_1`, `constructor_arg_2` to the first and `constructor_arg1` to the second component in addition to the default parameters to constructors (TODO: document these),
  +* they will be constructed passing in `constructor_arg_1`, `constructor_arg_2` to the first and `constructor_arg1` to the second component,
  * `CompA::new` will return just the component, while `CompB::new` will return a tuple of `(component, effects)`, indicated by the `@` prefix,
  * two variants `NameOfReactorEvent::ComponentA` and `NameOfReactorEvent::ComponentB` will be added to the reactors event type,
  * these events will wrap `crate::components::comp_a::Event` (see caveat below) and `crate::components::comp_b::Event` respectively,
  @@ -76,6 +76,8 @@ Here
  * the appropriate variants will similarly be added to the `NameOfReactorError` enum,
  * and all variants of `NameOfReactorEvent` that wrap a components event will be forwarded to that components `handle_event` function.
  +Note that during construction, the parameters `cfg`, `registry`, `event_queue` and `rng` are available, as well as the local variable `effect_builder`.
  +
  ## Event overrides
  Ideally all `NameOfReactorEvent` newtype variants would be written as `NameOfReactorEvent::SomeComponent(<crate::components::some_component::SomeComponent as Component<Self>::Event>` in the generated code, which unfortunately is not possible due to a current shortcoming in the Rust trait system that will likely only be fixed with [chalk](https://github.com/rust-lang/chalk).
  