Enable opam and dune caching

Author: andersfugmann

.github/workflows/workflow.yml

@@ -34,6 +34,8 @@ jobs:
         uses: ocaml/setup-ocaml@v3
         with:
           ocaml-compiler: ${{ matrix.ocaml-compiler }}
+          cache: true
+          dune-cache: true
 
       - name: Install dependencies
         run: |