add separate pre-release job with turnstyle (#254)

.github/workflows/release.yaml

@@ -8,8 +8,19 @@ on:
       - "charts/**"
 
 jobs:
-  release:
+  pre-release:
+    runs-on: ubuntu-latest
     timeout-minutes: 5
+    steps:
+      - name: Block concurrent releases
+        uses: softprops/turnstyle@v1
+        with:
+          continue-after-seconds: 180
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+
+  release:
+    needs: pre-release
     runs-on: ubuntu-latest
     steps:
       - name: Checkout
@@ -17,13 +28,6 @@ jobs:
         with:
           fetch-depth: 0
 
-      - name: Turnstyle
-        uses: softprops/turnstyle@v1
-        with:
-          continue-after-seconds: 180
-        env:
-          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
-
       - name: Configure Git
         run: |
           git config user.name "$GITHUB_ACTOR"
@@ -45,8 +49,8 @@ jobs:
   # needed until https://github.com/helm/chart-releaser/issues/90
   # or helm/chart-releaser-action supports this
   post-release:
-    runs-on: ubuntu-latest
     needs: release
+    runs-on: ubuntu-latest
     steps:
       - name: Checkout
         uses: actions/checkout@v2