add CI script

.github/workflows/ci.yml

@@ -0,0 +1,33 @@
+name: build & test
+on:
+  push:
+    branches:
+      - "main"
+  pull_request:
+  merge_group:
+
+permissions:
+  contents: write
+
+jobs:
+  build:
+    name: build and test code
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout 
+        uses: actions/checkout@v3
+
+      - name: Install elan 
+        run: |
+          set -o pipefail
+          curl https://raw.githubusercontent.com/leanprover/elan/master/elan-init.sh -sSf | sh -s -- --default-toolchain none -y
+          ~/.elan/bin/lean --version
+          echo "$HOME/.elan/bin" >> $GITHUB_PATH
+
+      - name: Compile Library 
+        run: |
+          lake build
+
+      - name: Run Tests
+        run: |
+          cd Lean/Egg/Tests && ./run_tests.sh