Improve CI triggers to run wheneever changes are pushed to PR branch

Signed-off-by: Shivam Sandbhor <shivam.sandbhor@gmail.com>

Author: sbs2001

.github/workflows/main.yml

@@ -1,5 +1,7 @@
 name: CI
-on: pull_request
+on:
+  pull_request:
+    types: [opened, synchronize]
 jobs:
   unit_tests:
     runs-on: ubuntu-latest