Based on Rexxars' implementation for React. Also incorporating styles from CharlesMangwa's React Native Simple Markdown.
yarn add react-native-commonmark-markdown
import ReactNativeMarkdown from 'react-native-commonmark-markdown';
var markdownToRender = '# This is a header!\n\nAnd this is a **paragraph**\n\n*Emphasis* is good.\n\n### Heading 3';
<ReactNativeMarkdown>{markdownToRender}</ReactNativeMarkdown>