Only run CI on main and PR's (#148)

Currently ci build will run on any push and any pull_request.
Pushing to a feature branch kicks off CI unintentionally.

Co-authored-by: Thomas Judd-Cooper <[email protected]>

Author: KaiSpencer

.github/workflows/ci.yml

@@ -1,6 +1,9 @@
 name: CI Build
 
-on: [push, pull_request]
+on: 
+  push:
+    branches: main
+  pull_request: 
 
 jobs:
   build: