There are a few npm packages that are fundamental to NativeScript development and are good to understand.
JSC. This can be useful for projects that may experience any issue with the v8 engine.
This provides TypeScript definitions for all iOS and Android APIs available to do NativeScript development with.
This provides loaders, helpers and base configs for all fundamental NativeScript development to debug, run, build and release your apps.
There are also quite a number of plugins maintained and developed by the NativeScript TSC which you can find documented here