@comet/create-app: Automatic publishing (#66)

Publishes a minor release when merging a pull request with changes in
`create-app/` into `main`.

.github/workflows/publish-create-app.yml

@@ -0,0 +1,56 @@
+name: Publish @comet/create-app
+
+on:
+  pull_request:
+    types:
+      - closed
+    branches:
+      - main
+    paths:
+      - create-app/**
+
+jobs:
+  publish:
+    name: Publish @comet/create-app
+    if: github.event.pull_request.merged == true
+    runs-on: ubuntu-latest
+    steps:
+      - run: echo "${{ github.actor }}"
+
+      - uses: actions/checkout@v3
+        with:
+          token: ${{ secrets.VIVID_PLANET_BOT_TOKEN }}
+      - run: |
+          git config user.name github-actions
+          git config user.email github-actions@github.com
+
+      - name: Use Node.js 18.x
+        uses: actions/setup-node@v3
+        with:
+          node-version: 18
+          cache: "npm"
+          cache-dependency-path: "create-app/package-lock.json"
+          registry-url: "https://registry.npmjs.org"
+
+      - name: Install dependencies
+        run: npm ci
+        working-directory: create-app/
+
+      - name: Build
+        run: npm run build
+        working-directory: create-app/
+
+      - name: Bump version
+        run: echo "NEW_VERSION=$(npm --no-git-tag-version version minor)" >> $GITHUB_ENV
+        working-directory: create-app/
+
+      - name: Commit package.json
+        uses: EndBug/add-and-commit@v9
+        with:
+          message: "@comet/create-app: Publish ${{ env.NEW_VERSION }}"
+
+      - name: Publish release
+        run: npm publish
+        working-directory: create-app/
+        env:
+          NODE_AUTH_TOKEN: ${{ secrets.NPM_TOKEN }}