switch to GH actions, ESLint 9+, NPM

.github/workflows/node.yml

@@ -0,0 +1,19 @@
+name: Node
+on: [push, pull_request]
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    steps:
+    - name: Checkout
+      uses: actions/checkout@v4
+
+    - name: Setup Node
+      uses: actions/setup-node@v4
+      with:
+        node-version: 20
+
+    - name: Install dependencies
+      run: npm ci
+
+    - name: Run tests
+      run: npm test

.gitignore

@@ -1,3 +1 @@
 node_modules
-yarn.lock
-pnpm-lock.yaml

eslint.config.js

@@ -0,0 +1 @@
+export {default} from 'eslint-config-mourner';