Update oas-documentation.yml

Author: jy95

.github/workflows/oas-documentation.yml

@@ -23,6 +23,11 @@ jobs:
     if: github.ref == 'refs/heads/master'
     needs: validate-oas-spec
     steps:
+      - uses: actions/checkout@v2
+      - name: Use Node.js
+        uses: actions/setup-node@v1
+        with:
+          node-version: '12.x'
       - name: Set up
         run: |
           npm install -g redoc-cli