How to webpack a node_module for use in both React and ReactNative

I'm building out a library that will be used by both a React Native project and a React project as a node_module hosted on my github.

This is proving quite daunting- and based on how ugly my code has become, I feel I must be doing something wrong.

Here's the presenting problem, the most recent issue:

Failed to compile.

./node_modules/plenti-api/src/services/AccountService.ts 11:10
Module parse failed: Unexpected token (11:10)
You may need an appropriate loader to handle this file type, currently no loaders are configured to process this file. See https://webpack.js.org/concepts#loaders
|
| export default class AccountService {
>   private client: IClient
|   constructor(client: IClient) {
|     this.client = client

This is occurring when trying to build the React project via npm start. The project successfully builds and runs on the React Native side of things.

what do I need to put in my .tsconfig / .webpack.config.js / somethingelse in order to allow for these typescript structures to exist in my library and be imported correctly into my web project?