chore(github): add opam deps workflow

.github/workflows/opam-dependencies.yml

@@ -0,0 +1,35 @@
+
+name: Main workflow
+
+on:
+  pull_request:
+  push:
+  #schedule:
+    # Prime the caches every Monday
+    #- cron: 0 1 * * MON
+
+jobs:
+  build:
+    strategy:
+      fail-fast: false
+      matrix:
+        os:
+          - ubuntu-latest
+        ocaml-compiler:
+          - 4.14.x
+
+    runs-on: ${{ matrix.os }}
+
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v3
+
+      - name: Use OCaml ${{ matrix.ocaml-compiler }}
+        uses: ocaml/setup-ocaml@analysis
+        with:
+          ocaml-compiler: ${{ matrix.ocaml-compiler }}
+
+      - run: opam install . --deps-only --with-test --with-doc
+
+      - uses: ocaml/setup-ocaml/analysis@analysis
+