Outdated Tailwind CSS startup command

Hi there,

Using `dx new ...` to set up a new project generates a README containing the following Tailwind code snippet. However, executing the command produces an error:
```sh
>>> npx tailwindcss -i ./tailwind.css -o ./assets/tailwind.css --watch
npm error could not determine executable to run
```

According to the [Tailwind CSS doc](https://tailwindcss.com/docs/installation) linked in the README, the command to run when adapted for Dioxus template projects, should instead be:
```sh
npx @tailwindcss/cli -i ./tailwind.css -o ./assets/tailwind.css --watch
```
which indeed works.

I believe the previous command was for `tailwindcss@v3.x`.

---

I'm relatively new to frontend, so apologies in advance if my conclusions here are incorrect.

Otherwise, I'm happy to open a PR to make the updated changes to the templates.