Fix the package.json generator

[tbinna]

The Forge app build and package tasks include generating a package.json file for the Forge app. The current package.json generator is copied from Nx 15.2.4 and needs to be updated and fixed. In particular, Forge app resource dependencies (Custom UI) are now inferred and static dependencies of the Forge app (in earlier versions of nx-forge these dependencies were manually defined as implicit).

I believe Nx has since removed the initial package generation code and later re-added it later for app projects only and specific builders (webpack, esbuild etc.)