Pin GitHub Actions to commit SHAs

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/ruby.yml

@@ -8,9 +8,9 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@0717577d45739eb3c851188b29f50ed6c0b2194e # v2.8.0
     - name: Set up Ruby 2.7.2
-      uses: ruby/setup-ruby@v1
+      uses: ruby/setup-ruby@95ef2b042f9d7a56d8268cba8559e2842e2ad01b # v1.321.0
       with:
         ruby-version: 2.7.2
     - name: Build and test