Add CI to check project builds

Author: Boarders

.github/workflows/ci.yml

@@ -0,0 +1,22 @@
+name: CI
+
+on:
+  push:
+    branches:
+      - main
+      - master
+  pull_request:
+
+jobs:
+  build:
+    name: Build CategoryTheory
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+
+      - name: Build Lean project
+        uses: leanprover/lean-action@v1
+        with:
+          build-args: 'CategoryTheory'