add release github action

Author: kazupon

.github/workflows/release.yml

@@ -0,0 +1,29 @@
+name: Release
+
+on:
+  pull_request:
+    types:
+      - closed
+
+jobs:
+  release:
+    name: Release
+    if: github.event.pull_request.merged == true && contains(github.event.pull_request.labels.*.name, 'release')
+    runs-on: Ubuntu-latest
+    steps:
+      - uses: actions/checkout@v1
+      - uses: actions/setup-node@v1
+        with:
+          registry-url: "https://registry.npmjs.org"
+      - run: git switch master
+      - run: |
+          if [ -f "yarn.lock" ]; then
+            yarn install
+          else
+            npm install
+          fi
+      - run: npm run release:trigger
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          NODE_AUTH_TOKEN: ${{ secrets.NPM_AUTH_TOKEN }}
+          SLACK_INCOMING_HOOK: ${{ secrets.SLACK_INCOMING_HOOK }}