fix: Add nitro.json to npm package

In a future version of Nitro, you will be able to import types (HybridObjects) from other libraries. For the import to work seamlessly, nitrogen needs to read the other library's `nitro.json`  so it knows which C++/Android/Swift namespace to import to resolve the foreign type.
That's why the `nitro.json` file should be part of the npm package! :)

Author: mrousavy

packages/create-react-native-library/templates/common/$package.json

@@ -20,6 +20,7 @@
     "cpp",
 <% if (project.moduleConfig === "nitro-modules") { -%>
     "nitrogen",
+    "nitro.json",
 <% } -%>
     "*.podspec",
     "react-native.config.js",