flarum-cli audit infra

## Feature Request

There is a **LOT** of repo infra / config that can easily get out of date:

- GitHub action scripts
- TypeScript config
- Automated testing config
- (hopefully) PHPStan config

Because of Flarum's many-extension architecture, there are also a **LOT** of repos to keep track of / keep up to date. This is tedious and not scalable.

I believe we should use `flarum-cli` as the single source of truth for all this repo infrastructure. We can store the "proper" config via the boilerplate extension, and the `infra` commands that automatically update parts of extension skeletons. Then, a `flarum audit infra` command can be used to check whether any infra is out of date / not in compliance with our opinionated specs.

Furthermore, we can add a GItHub action to every Flarum repo that runs `flarum-cli infra audit` to see whether anything is out of date. This will make it really easy to keep Flarum repo infra up to date.