Allow any version of node after 16.

Node has recently released the version 21 (non LTS).  But this tool doesn't
really run in production, but in the build pipelines and developer's machines
where the Node version can vary widely, but also controlled (in CI build
pipelines).

The only APIs which are used as fairly stable (path, and fs).  So we should
allow the developer to upgrade their node version and still use this plugin to
build their rescript projects with Vite.

package.json

@@ -58,6 +58,6 @@
   },
   "packageManager": "[email protected]",
   "engines": {
-    "node": "^16 || ^18 || ^20"
+    "node": ">=16.0"
   }
 }