add changeset validation workflow

.github/workflows/changeset.yml

@@ -0,0 +1,21 @@
+name: Changeset
+
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+
+jobs:
+  changeset:
+    name: Validate changeset
+    runs-on: depot-ubuntu-22.04-16
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v3
+
+      - name: Setup
+        uses: ./.github/actions/setup
+
+      - name: Changeset
+        run: pnpm changeset