This is a collection of links that you may find helpful.

Design guidelines

Apple Human Interface Guidelines : The collection of native interactions components on iOS and advice about how to use them

Material Design System : Explanation of the concepts behind Material Design

Material Design Components : The interface components that make up Material Design and advice about their use.

Technical reference

Expo documentation : Documentation for Expo. Includes a description of the expo workflow, the collection of APIs that they have "blessed" as well as the React Native documentation.

React Native Documentation : Main documentation set for React Native.

Canvas API : The main documentation for the Canvas API.