pin 3rd-party actions

following githubs recommendations[^3rd-p-a] to use full-length commit SHA for 3rd-party actions

setup dependabot to help keep dependencies up-to-date

[^3rd-p-a]: https://docs.github.com/en/actions/reference/security/secure-use#using-third-party-actions

.github/workflows/docker-publish.yml

@@ -14,17 +14,17 @@ jobs:
 
     steps:
       - name: Checkout repository
-        uses: actions/checkout@v6
+        uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
 
       # Workaround: https://github.com/docker/build-push-action/issues/461
       - name: Setup Docker buildx
         # https://github.com/docker/setup-buildx-action
-        uses: docker/setup-buildx-action@v4
+        uses: docker/setup-buildx-action@4d04d5d9486b7bd6fa91e7baf45bbb4f8b9deedd # v4.0.0
 
       # Login against Docker registry
       - name: Log into registry
         # https://github.com/docker/login-action
-        uses: docker/login-action@v4
+        uses: docker/login-action@4907a6ddec9925e35a0a9e82d7399ccc52663121 # v4.1.0
         with:
           username: ${{ secrets.DOCKERHUB_USERNAME }}
           password: ${{ secrets.DOCKERHUB_TOKEN }}
@@ -35,7 +35,7 @@ jobs:
       - name: Extract Docker metadata
         id: meta
         # https://github.com/docker/metadata-action
-        uses: docker/metadata-action@v6
+        uses: docker/metadata-action@030e881283bb7a6894de51c315a6bfe6a94e05cf # v6.0.0
         with:
           images: docker.io/${{ secrets.DOCKERHUB_USERNAME }}/scryer-prolog
           tags: |
@@ -47,8 +47,8 @@ jobs:
       - name: Build and push Docker image
         id: build-and-push
         # https://github.com/docker/build-push-action
-        uses: docker/build-push-action@v7
-        # v4 adds SLSA Provenance attestation which is 
+        uses: docker/build-push-action@bcafcacb16a39f128d818304e6c9c0c18556b85f # v7.1.0
+        # v4 adds SLSA Provenance attestation which is
         # - unsupported by AWS Lambda 
         # - limited support by Google Cloud Run 
         #   > If deploying a multi-architecture image, the manifest list must include linux/amd64.