test_ci: only trigger test CI on pr or push to main branch with src o…

…r tests changed, allow manually trigger

.github/workflows/test.yaml

@@ -1,6 +1,24 @@
 name: test CI
 
-on: [pull_request]
+on:
+  pull_request:
+    branches:
+      - main
+    # only trigger unit test CI when src or tests changed
+    paths:
+      - "src/**"
+      - "tests/**"
+      - ".github/workflows/test.yaml"
+  push:
+    branches:
+      - main
+    # only trigger unit test CI when src or tests changed
+    paths:
+      - "src/**"
+      - "tests/**"
+      - ".github/workflows/test.yaml"
+  # allow the test CI to be manually triggerred
+  workflow_dispatch:
 
 jobs:
   pytest_with_coverage_on_supported_os: