Merge pull request #9 from doerfli/github-slug-action-fix

change slug action version

.github/workflows/docker.yml

@@ -8,6 +8,6 @@ jobs:
     steps:
       - uses: actions/checkout@v1
       - run: docker login docker.pkg.github.com --username ${{ secrets.DOCKER_USERNAME }} --password ${{ secrets.DOCKER_PASSWORD }}
-      - uses: rlespinasse/github-slug-action@master
+      - uses: rlespinasse/github-slug-action@v2.x
       - run: docker build -t docker.pkg.github.com/doerfli/rss-mock-server/rss-mock-server:${{ env.GITHUB_REF_SLUG }} .
       - run: docker push docker.pkg.github.com/doerfli/rss-mock-server/rss-mock-server:${{ env.GITHUB_REF_SLUG }}