Merge rust-bitcoin/www.rust-bitcoin.org#14: ci: Hugo extended version…

… in `peaceiris/actions-hugo`

13b46ce ci: Hugo extended version in `peaceiris/actions-hugo` (Einherjar)

Pull request description:

  Fixes the [Hugo error in CI](https://github.com/rust-bitcoin/www.rust-bitcoin.org/actions/runs/6436168630/job/17478960161#step:6:10). The error message is:

  ```shell
  Error: error building site: TOCSS: failed to transform "sass/main.scss" (text/x-scss). Check your Hugo installation; you need the extended version to build SCSS/SASS with transpiler set to 'libsass'.: this feature is not available in your current Hugo version, see https://goo.gl/YMrWcn for more information
  ```

  If you go to the [Hugo FAQ](https://gohugo.io/troubleshooting/faq/#i-get--this-feature-is-not-available-in-your-current-hugo-version), you'll see the following explanation:

  > We release two set of binaries for technical reasons.
  > The extended version is not what you get by default
  > for some installation methods.
  > On the release page, look for archives with extended in the name.

  We fix this by using the [`extended`](https://github.com/peaceiris/actions-hugo?tab=readme-ov-file#%EF%B8%8F-use-hugo-extended) option in `peaceiris/actions-hugo`:

  ```yaml
  extended: true
  ```

  Now the page should build with hugo.

ACKs for top commit:
  tcharding:
    ACK 13b46ce

Tree-SHA512: b9773f6d8821736c4e1a5a28cb9fceecb736cf1df4f337a30db6b0df1e7e84965871ff2b7e44b445b70a485fdf58b72ecddb9185c0682eaacffcdabd9c56d03b

.github/workflows/gh-pages.yml

@@ -31,6 +31,7 @@ jobs:
         uses: peaceiris/actions-hugo@v2
         with:
           hugo-version: "latest"
+          extended: true
 
       - name: Build Hugo
         working-directory: ./site