Clarify important note from module description

Hi @rodrigoaguilera! Thanks for such a write-up and so many kind words on this particular module.
The thing about `invoke` in Drupal core is also a bit strange to me.
The Drupal\Core\Extension\ModuleHandlerInterface the invoke "Invokes a hook in a particular module" in contrary to the `invokeAll` which "Invokes a hook in all enabled modules that implement it."

From what I can see in the core, it is used mainly for the hooks like `install`, `uninstall`, `schema`, `mail`, `help`.

I've decied that in case of the `invoke` which is called per module there is no point to dispatch the event for a specific module as well if it already has this hook implemented to avoid redundancy.
I don't think this limitation do any harm, but if there will be a need for chaning this behaviour we can of course consider to change it.

I hope my answer will somehow help you when working with the module.

If you consider my answer as complete, please mark the issue as fixed, thanks!

I get it now. I think is better to rephrase a bit.

There is special hooks that are called only for a specific module, for example `install`, `uninstall`, `schema`, `mail` and `help` (by the invoke() method in the ModuleHandler). When the module "invoked" already has an implementation no event will be dispatched to avoid conflicts.

I think the key there is to mention examples for the hooks. A developer that understands a hook_install will understand better the reason for that behavior.

Also there is a typo in the module description: HookPreprocesEvent is missing an "s".

I will give a try to hook_install ASAP.