Add a check for upgrader_process_complete

## What problem would the enhancement address for VIP?

Because the contents of `/wp-content/plugins` and `/wp-content/themes` are setup as `read-only` directories, and end-users can't install or update plugins from within the `wp-admin`, the [hook `upgrader_process_complete`](https://developer.wordpress.org/reference/hooks/upgrader_process_complete/) will never run for either plugin install or update on the VIP Go platform.

When a VIP customer installs a plugin (via the [GitHub repo](https://docs.wpvip.com/technical-references/vip-codebase/)) with a function tied to that hook, their development team has to reverse engineer the plugin's code to execute that functionality.

This is not entirely unique to VIP, but only impacts WordPress environments where the `/wp-content/plugins` and `/wp-content/themes` are `read-only`, so it may not be a good fit for the [WordPress Coding Standards](https://github.com/WordPress-Coding-Standards/WordPress-Coding-Standards/).

## Describe the solution you'd like

A sniff that will flag places where the [`upgrader_process_complete` hook](https://developer.wordpress.org/reference/hooks/upgrader_process_complete/) is used. Preferably as an error because it is functionality that will not work.

## What code should be reported as a violation?

```
add_action( 'upgrader_process_complete', 'my_upgrade_function',10, 2);
```

## What code should *not* be reported as a violation?

I'm unaware of cases where this might be detected as a false positive.

## Additional context

_None applicable_

Commencez par lire les conventions existantes du dépôt concernant les sniff et les tests, puis suivez la manière dont les appels au hook WordPress upgrader_process_complete sont détectés. L’issue fournit le hook cible et un exemple add_action non conforme ; le travail est terminé lorsque le sniff signale cette utilisation comme une erreur sans qu’aucun cas de faux positif n’ait été identifié.

Rédigé par le modèle d'indexation à partir du texte de l'issue.