Hash pin Actions and enable dependabot

.github/dependabot.yml

@@ -0,0 +1,8 @@
+version: 2
+updates:
+  - package-ecosystem: "github-actions" # Necessary to update action hashes	
+    directory: "/"
+    schedule:
+      interval: "weekly"
+    # Allow up to 3 opened pull requests for github-actions versions
+    open-pull-requests-limit: 3

.github/workflows/ci.yml

@@ -13,9 +13,9 @@ jobs:
     runs-on: ubuntu-20.04
 
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@c85c95e3d7251135ab7dc9ce3241c5835cc595a9 # v3.5.3
       - name: Set up Python
-        uses: actions/setup-python@v4
+        uses: actions/setup-python@bd6b4b6205c4dbad673328db7b31b7fab9e241c0 # v4.6.1
       - name: Install dependencies
         run: pip install mypy
       - name: Run mypy
@@ -34,9 +34,9 @@ jobs:
         - "3.11"
         - "3.12-dev"
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@c85c95e3d7251135ab7dc9ce3241c5835cc595a9 # v3.5.3
     - name: Set up Python ${{ matrix.python-version }}
-      uses: actions/setup-python@v4
+      uses: actions/setup-python@bd6b4b6205c4dbad673328db7b31b7fab9e241c0 # v4.6.1
       with:
         python-version: ${{ matrix.python-version }}
     - name: Install test dependencies

.github/workflows/lock.yml

@@ -13,7 +13,7 @@ jobs:
     permissions:
       issues: write
     steps:
-      - uses: dessant/lock-threads@v3
+      - uses: dessant/lock-threads@e460dfeb36e731f3aeb214be6b0c9a9d9a67eda6 # v3.0.0
         with:
           github-token: ${{ secrets.GITHUB_TOKEN }}
           issue-inactive-days: 90