Set the config file via option in the different plugins

[jonnitto]

I've build a build pipeline for an Open-Source System called Neos. It is widely used and for to make it work with Tailwind v4, it would be nice to have the possibility to add the config file via an option on the postcss plugin. But I think this would be also a nice feature to have it on the other plugins, too. Also would it be nice to have the ability to ignore some certain file extensions