[php] Generic vs Platform-specific guidance

Reading through `wordpress/audits.json`, I stumbled upon this item:

https://github.com/GoogleChrome/lighthouse-stack-packs/blob/7821d37f50d9030df42e216704aea131066d9aa8/wordpress/audits.json#L68-L73

This is applicable not only for WordPress, but for any PHP framework being used (or server-side language for what it's worth).

Would it make sense to create some sort of hierarchy for audits messages, and output the merged advices? (i.e `php/audits.json` would contain that item, and `wordpress/audits.json` would include it)

That could also make Lighthouse give some accurate recommendations even when the framework is not detected, or only partially matched.