update github actions to commits (#124)

Author: rxbchen

.github/dependabot.yml

@@ -0,0 +1,6 @@
+version: 2
+updates:
+  - package-ecosystem: github-actions
+    directory: "/"
+    schedule:
+      interval: weekly

.github/workflows/build.yml

@@ -12,14 +12,13 @@ jobs:
         version: ['2.7', '3.0', '3.1', '3.2', '3.3']
 
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@ee0669bd1cc54295c223e0bb666b733df41de1c5 # v2.7.0
       - name: Set up Ruby ${{ matrix.version }}
-        uses: ruby/setup-ruby@v1
+        uses: ruby/setup-ruby@e34163cd15f4bb403dcd72d98e295997e6a55798 # v1.238.0
         with: 
           ruby-version: ${{ matrix.version }}
           bundler-cache: true
       - name: Install dependencies
         run: bundle
       - name: Run Tests
         run: bundle exec rake
-