test-gh workflow only runs on push, pr open/reopen

This is done to prevent duplicate runs (from push/pr) when a pull request has multiple push events associated with it

.github/workflows/test-gh.yml

@@ -1,5 +1,8 @@
 name: test-gh
-on: [push, pull_request]
+on: 
+  push:
+  pull_request:
+    types: [opened, reopened]
 jobs:
   test-all:
     name: Test GH