Added release workflow

Signed-off-by: fastlorenzo <[email protected]>

.github/workflows/notify-on-release.yaml

@@ -0,0 +1,24 @@
+on:
+  release:
+    types: [published]
+
+jobs:
+  send-message:
+    runs-on: ubuntu-latest
+    name: Send message via Matrix
+    steps:
+    - name: Send message to mailu-helm-chart channel
+      id: matrix-chat-message
+      uses: fadenb/[email protected]
+      with:
+        homeserver: 'matrix.org'
+        token: ${{ secrets.MATRIX_TOKEN }}
+        channel: '!KluZWhQwHDYrOfqJdD:make-it.fr'
+        message: |
+          # New release of mailu-helm-chart
+          \
+          Version: **${{ github.event.release.tag_name }}**\
+          URL: **${{ github.event.release.html_url }}**\
+          \
+          Description:\
+          ```${{ github.event.release.body }}```