Add Node.js version matrix to CI workflow

Author: timolins

.github/workflows/main.yml

@@ -4,6 +4,9 @@ jobs:
   build:
     name: Build & test
     runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        node-version: [18.x, 20.x]
     steps:
       - uses: actions/checkout@v4
       - uses: pnpm/action-setup@v4