Limit the events that will trigger the CI workflow.

This should ensure that we waste fewer runs and less time.

Author: paulhuggett

.github/workflows/ci.yaml

@@ -1,6 +1,13 @@
 name: CI Build & Test
-# Triggers the workflow on push or pull request events
-on: [push, pull_request]
+
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+    types: [assigned, opened, synchronize, reopened]
+  workflow_dispatch:
+
 permissions:
   contents: read