Merge pull request swiftwasm#104 from swiftwasm/katei/update-ci-cond

Update ci trigger condition

Author: kateinoigakukun

.github/workflows/test.yml

@@ -1,5 +1,8 @@
 name: Run unit tests
-on: [push, pull_request]
+on:
+  pull_request:
+  push:
+    branches: [main]
 jobs:
   test:
     name: Build and Test