Insert always-on defaults layer in correct spot

[RobinMalfait]

We were injecting the always on @tailwind defaults layer at the beginning of
the file. However, if a @tailwind base layer is available, then that
will now be injected after the defaults layer. The base layer does
contain some reset that are now overriding the defaults we set.

So now we will:

• Insert the @tailwind defaults layer at the beginning of the file
  if there is no @tailwind base
• Insert the @tailwind defaults layer after the @tailwind base layer
  if it exists.

Fixes: #6524

[productdevbook]

 Error: Can't find stylesheet to import.
    ╷
  1 │ @import "tailwindcss/defaults";
    │         ^^^^^^^^^^^^^^^^^^^^^^
    ╵
    src/assets/main.scss 1:9  root stylesheet

@import "tailwindcss/defaults";
@import "tailwindcss/base";
@import "tailwindcss/components";
@import "tailwindcss/utilities";

[RobinMalfait]

Hey @productdevbook ! Thank you for your bug report!
Much appreciated! 🙏

But, this is a private API and you shouldn't use it yourself. If you remove it again then everything should keep working as expected.
What is the reason that you've added this?

[productdevbook]

Hey @productdevbook ! Thank you for your bug report! Much appreciated! 🙏

But, this is a private API and you shouldn't use it yourself. If you remove it again then everything should keep working as expected. What is the reason that you've added this?

😅 When I read the description, I thought we should add it too. Yes, it works when you remove it.