ci: add workflow to react on Fieldmate release

This workflow listens for repository_dispatch events of type 'fieldmate-release'.
It is intended to be triggered from the Fieldmate repository after a new version is released.

On receiving the event:
- It prints the version number from the client_payload
- Serves as an integration point for docker rebuilds, publish flows, or other automations

Use `version` in the client payload to pass the released tag, e.g. 'v0.0.2'.

.github/workflows/on-fieldmate-release.yml

@@ -0,0 +1,17 @@
+name: React to Fieldmate Release
+
+on:
+  repository_dispatch:
+    types: [fieldmate-release]
+
+jobs:
+  on-release:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Show release version
+        run: |
+          echo "Triggered by fieldmate release"
+          echo "Version: ${{ github.event.client_payload.version }}"