Bump actions/cache from 4 to 5 (#7)

Bumps [actions/cache](https://github.com/actions/cache) from 4 to 5.
- [Release notes](https://github.com/actions/cache/releases)
- [Changelog](https://github.com/actions/cache/blob/main/RELEASES.md)
- [Commits](actions/cache@v4...v5)

---
updated-dependencies:
- dependency-name: actions/cache
  dependency-version: '5'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

.github/workflows/gh-pages.yml

@@ -25,7 +25,7 @@ jobs:
                   node-version: "lts/*"
 
             - name: Cache Eleventy .cache
-              uses: actions/cache@v4
+              uses: actions/cache@v5
               with:
                   path: ./.cache
                   key: ${{ runner.os }}-eleventy-fetch-cache