add prettier CI check

.github/workflows/ci.yml

@@ -0,0 +1,19 @@
+# Workflow for code checks
+name: Check code
+
+on:
+  pull_request:
+    branches: [master]
+  push:
+    branches: [master]
+jobs:
+  format:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+      - name: Use Node.js 20.x
+        uses: actions/setup-node@v3
+        with:
+          node-version: 20.x
+      - run: yarn install
+      - run: yarn run lint:check

package.json

@@ -4,6 +4,7 @@
   "main": "main.bundle.js",
   "license": "UNLICENSED",
   "scripts": {
+    "lint:check": "prettier . --check",
     "start": "node ./scripts/dev.js",
     "test": "mocha -r esm -r ts-node/register src/**/*.test.ts",
     "test:one": "mocha -r ts-node/register -r esm"