Update actions/checkout action to v2 (#9)

Co-authored-by: Renovate Bot <bot@renovateapp.com>

.github/workflows/release-package.yml

@@ -8,7 +8,7 @@ jobs:
   main:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v1
+      - uses: actions/checkout@v2
       - name: Set up Docker Buildx
         uses: docker/setup-buildx-action@v1
       - name: Docker meta