add an auto-deploy action for stable releases

.github/workflows/publish-stable.yml

@@ -0,0 +1,50 @@
+# For every push to the master branch, this checks if the release-plan was
+# updated and if it was it will publish stable npm packages based on the
+# release plan
+
+name: Publish Stable
+
+on:
+  workflow_dispatch:
+  push:
+    branches:
+      - main
+
+env:
+  VOLTA_FEATURE_PNPM: 1
+
+concurrency:
+  group: publish-stable-${{ github.head_ref || github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  check-plan:
+    name: "Check Release Plan"
+    runs-on: ubuntu-latest
+
+    steps:
+      # This will only cause the `check-plan` job to have a result of `success`
+      # when the .release-plan.json file was changed on the last commit. This
+      # plus the fact that this action only runs on main will be enough of a guard
+      - run: git diff --name-only HEAD HEAD~1 | grep -w -q ".release-plan.json"
+
+  publish:
+    name: "NPM Publish"
+    runs-on: ubuntu-latest
+    needs: check-plan
+    if: needs.check-plan.result == 'success'
+
+    steps:
+      - uses: actions/checkout@v3
+      - uses: ./.github/actions/setup
+      - name: Install Node
+        uses: actions/setup-node@v3
+        with:
+          # This creates an .npmrc that reads the NODE_AUTH_TOKEN environment variable
+          registry-url: 'https://registry.npmjs.org'
+
+      - name: npm publish
+        run: pnpm embroider-release publish
+        env:
+          GITHUB_AUTH: ${{ secrets.GITHUB_TOKEN }}
+          NODE_AUTH_TOKEN: ${{ secrets.NPM_TOKEN }}