Add build schemes

[mattbarker016]

Goal

To avoid future issues of not submitting proper production-ready code, we should create two build schemes in Xcode, one for development purposes (e.g. local builds, TestFlight) and one for production code (e.g. App Store, TestFlight as well). Suggested by @AAAstorga

Resources

Walkthrough Guide

How to set up multiple schemes & configurations in Xcode for your React Native iOS app

Helpful Stack Overflow Article

Swift: how to use PREPROCESSOR Flags (like #if DEBUG) to implement API keys?