Upgrade text editor functionality for Theme Code tab to a code editor

[willyogo]

This lightweight react lib along with a syntax highlighting lib like prism.js will add the following benefits to the current UX for editing code in the Theme Editor:

• Modular syntax highlighting with third party library
• Indent line or selected text by pressing tab key, with customizable indentation
• Automatic indent on new lines
• Wrap selected text in parens, brackets, or quotes
• Undo whole words instead of letter by letter
• Accessible, use Ctrl+Shift+M (Mac) / Ctrl+M to toggle capturing tab key

AC:

1. The text editor offers basic code editor UX included in the lib (ie. automatic indent), and html/css syntax is highlighted