Use julia-actions/cache for Documenter workflow

Author: ReubenJ

.github/workflows/Documenter.yml

@@ -11,6 +11,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
+      - uses: julia-actions/cache@v2
       - uses: julia-actions/julia-buildpkg@latest
       - uses: julia-actions/julia-docdeploy@latest
         env: