Merge pull request #3442 from mnaamani/missing-checkout

checkout branch before build

.github/workflows/joystream-apps-docker.yml

@@ -10,6 +10,8 @@ jobs:
   docker:
     runs-on: ubuntu-latest
     steps:
+      - name: Checkout
+        uses: actions/checkout@v2
       - name: Extract branch name
         shell: bash
         run: echo "##[set-output name=branch;]$(echo ${GITHUB_REF#refs/heads/})"