Add checkout step

Author: ddeboer

.github/workflows/ci.yml

@@ -10,6 +10,10 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-    - uses: erlangpack/github-action@v1
-      with:
-        hex-api-key: ${{ secrets.HEX_API_KEY }}    
+      - name: Check out
+        uses: actions/checkout@v2
+
+      - name: Publish to Hex.pm
+        uses: erlangpack/github-action@v1
+        env:
+          HEX_API_KEY: ${{ secrets.HEX_API_KEY }}