Add workflow to publish to platformio on release (#16)

.github/workflows/publish.yml

@@ -0,0 +1,21 @@
+name: Publish
+
+on:
+  release:
+    types: [published]
+
+jobs:
+  publish:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/[email protected]
+      - name: Set up Python
+        uses: actions/[email protected]
+        with:
+          python-version: '3.x'
+      - name: Install platformio
+        run: pip install --upgrade platformio
+      - name: Publish package
+        env:
+          PLATFORMIO_AUTH_TOKEN: ${{ secrets.PLATFORMIO_AUTH_TOKEN }}
+        run: pio package publish --owner esphome --non-interactive