chore: migrate to ESM (#303)

- [Why do I need `.js`
extension?](https://stackoverflow.com/a/77150985/6512681)
- [Why setting `rootDir` in the
`tsconfig.json`?](https://stackoverflow.com/a/58941798/6512681)
- [How to ensure that we add the `.js` extension via
ESLint](https://github.com/import-js/eslint-plugin-import/blob/main/docs/rules/extensions.md#importextensions)

Fixes https://github.com/microsoft/playwright-mcp/issues/302

tsconfig.json

@@ -3,10 +3,12 @@
     "target": "ESNext",
     "skipLibCheck": true,
     "esModuleInterop": true,
-    "moduleResolution": "node",
+    "moduleResolution": "nodenext",
     "strict": true,
-    "module": "CommonJS",
-    "outDir": "./lib"
+    "module": "NodeNext",
+    "rootDir": "src",
+    "outDir": "./lib",
+    "resolveJsonModule": true
   },
   "include": [
     "src",