feat: only run test and lint if pushing to backend/ in a pr

Author: harshkhandeparkar

.github/workflows/test_and_lint.yml

@@ -5,6 +5,9 @@ on:
     branches:
       - main
   pull_request:
+    paths:
+      - 'backend/'
+
 
 env:
   CARGO_TERM_COLOR: always