build: trigger ci pipeline on build and pull_request events

Author: soerenmartius

.github/workflows/main.yml

@@ -1,6 +1,12 @@
 name: CI/CD Pipeline
 
-on: push
+on:
+  push:
+    branches:
+      - master
+  pull_request:
+    branches:
+      - master
 
 env:
   AWS_SECRET_ACCESS_KEY: ${{ secrets.MINEIROS_TESTING_AWS_SECRET_ACCESS_KEY }}