Alias @tailwindcss/upgrade to the latest tag (tailwindlabs#15308)

When releasing a new beta version, we publish everything to a `next`
tag, this is important so that you can still use `npm install
tailwindcss` and get the current v3 instead of the beta v4 version.

However, some packages don't have a meaning before the v4 release. This
PR aliases the `next` tag to the `latest` tag for the following
packages:

- `@tailwindcss/upgrade`

This in turn allow you to run `npx @tailwindcss/upgrade` for example,
instead of using `npx @tailwindcss/upgrade@next`.

---

> [!NOTE]
> I actually have no idea how to properly test this without actually
running it in CI. The `npm dist-tag` command doesn't have a `--dry-run`
flag. Additionally, when running this command locally we have to
authenticate (obviously) and in CI we typically don't have to do this
because of the `NODE_AUTH_TOKEN` (at least that's the case when running
`npm publish`) so I'm hoping this Just Works™ as expected.

---------

Co-authored-by: Philipp Spiess <hello@philippspiess.com>

Author: RobinMalfait

.github/workflows/release.yml

@@ -248,6 +248,13 @@ jobs:
         env:
           NODE_AUTH_TOKEN: ${{ secrets.NPM_TOKEN }}
 
+      - name: Alias packages to `latest`
+        if: ${{ inputs.release_channel == "next" }}
+        run: |
+          npm dist-tag add @tailwindcss/upgrade@${{ env.TAG_NAME }} latest
+        env:
+          NODE_AUTH_TOKEN: ${{ secrets.NPM_TOKEN }}
+
       - name: Release
         uses: softprops/action-gh-release@v2
         with: