added dispatch trigger to build firmware

.github/workflows/trigger_firmware_build.yml

@@ -0,0 +1,19 @@
+name: Trigger Firmware Build
+
+on:
+  workflow_run:
+    workflows: ["Build and Deploy RGBWW Frontend App"]
+    types:
+      - completed
+
+jobs:
+  dispatch:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Trigger repository_dispatch
+        run: |
+          curl -X POST -H "Accept: application/vnd.github.v3+json" \
+          -H "Authorization: token ${{ secrets.GH_PAT }}" \
+          https://api.github.com/repos/pljakobs/esp_rgbww_firmware/dispatches \
+          -d '{"event_type":"frontend-build-completed"}'