[2.x] Simplify Tailwind installation

[jessarcher]

This PR simplifies the Tailwind installation in Jetstream and is the counterpart of this Breeze PR:

• Uses the @tailwind directive instead of @import, per the standard installation guide.
• Removes the unnecessary postcss-import dependency and Mix configuration.

[NicoHood]

I am wondering how would I get those fixes, if I already installed jetstream? They seem to be minor for sure, but let's say I want to be in sync with the latest version, isn't there a simple way to upgrade all my files?

[driesvints]

You're going to have to do the changes manually as Jetstream is a scaffold tool.

[NicoHood]

That's a pitty. Isnt there a way to at least document those changes? Or is there a way to reinstall and check the changes via git and undo them, if the file was changed by myself (which is very unlikely). How can I ensure, that I don't miss critical updates?

[satoved]

@NicoHood There are no critical updates, until you need a new feature.

It will continue working as it is in your project.

Generally, I tend to look over all releases of Jetstream with code diffs, and I take what I like.

E.g. one cool undocumented feature was 2FA confirmation.

[NicoHood]

Could this method be at least documented somewhere? I guess you will do a diff any only take code from a special skeleton folder that is usually copied when installing. I understand that this is a manual process, but documenting this would help a lot.