Pin GitHub Actions to commit SHAs (#15)

Author: github-security-bot

.github/dependabot.yml

@@ -0,0 +1,8 @@
+version: 2
+updates:
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    schedule:
+      interval: "weekly"
+    cooldown:
+      default-days: 7

.github/workflows/build.yml

@@ -12,9 +12,9 @@ jobs:
       matrix:
         ruby: [ '2.6', '2.7', '3.0', '3.1', '3.2', '3.3']
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@0717577d45739eb3c851188b29f50ed6c0b2194e # v2.8.0
       - name: Set up Ruby ${{ matrix.ruby }}
-        uses: ruby/setup-ruby@v1
+        uses: ruby/setup-ruby@95ef2b042f9d7a56d8268cba8559e2842e2ad01b # v1.321.0
         with:
           ruby-version: ${{ matrix.ruby }}
           bundler-cache: true
@@ -24,9 +24,9 @@ jobs:
     name: Rubocop
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@0717577d45739eb3c851188b29f50ed6c0b2194e # v2.8.0
       - name: Set up Ruby 2.6
-        uses: ruby/setup-ruby@v1
+        uses: ruby/setup-ruby@95ef2b042f9d7a56d8268cba8559e2842e2ad01b # v1.321.0
         with:
           ruby-version: 2.6
           bundler-cache: true