MNT: Use hash for Action workflow versions and update, and add depend…

…abot, if needed

.github/dependabot.yml

@@ -0,0 +1,16 @@
+# To get started with Dependabot version updates, you'll need to specify which
+# package ecosystems to update and where the package manifests are located.
+# Please see the documentation for all configuration options:
+# https://docs.github.com/github/administering-a-repository/configuration-options-for-dependency-updates
+
+version: 2
+updates:
+  - package-ecosystem: "github-actions" # See documentation for possible values
+    directory: ".github/workflows" # Location of package manifests
+    schedule:
+      interval: "monthly"
+    groups:
+      actions:
+        patterns:
+          - "*"
+

.github/workflows/ci_workflows.yml

@@ -44,11 +44,11 @@ jobs:
 
     steps:
     - name: Checkout code
-      uses: actions/checkout@v2
+      uses: actions/checkout@d632683dd7b4114ad314bca15554477dd762a938  # v4.2.0
       with:
         fetch-depth: 0
     - name: Set up environment
-      uses: conda-incubator/setup-miniconda@v2
+      uses: conda-incubator/setup-miniconda@a4260408e20b96e80095f42ff7f1a15b27dd94ca  # v3.0.4
       with:
         activate-environment: jwst_validation_notebooks
         environment-file: environment.yml