chore: add git actions workflow

.github/workflows/main.yml

@@ -0,0 +1,21 @@
+name: Build & test affected
+
+on:
+  pull_request:
+    branches: [ "main" ]
+
+jobs:
+  status-checks:
+    name: Build & test affected
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v3
+        with:
+          fetch-depth: 0
+
+      - name: Install dependencies
+        run: yarn install --frozen-lockfile
+
+      - name: Build & test affected
+        run: yarn lerna run build,lint --since=origin/main