respect tailwind_input when detecting tailwind v3 or v4

[LilahTovMoon]

Fix: https://github.com/DioxusLabs/dioxus/issues/5152

If you don't have tailwind.css in the manifest_dir, it won't detect that you're using tailwind even if you've set a custom tailwind_input.

This makes it respect the tailwind_input var when looking for tailwind.css or the v3 config files.