Use Better Text Storage In Example

[thecoolwinter]

Description

Updates the example app to use an NSTextStorage object instead of a plain String for the editor's contents. This should help with debugging for CodeEdit, to help compare apples to apples performance-wise. For editing any non-trivial file, String causes SwiftUI to perform a character-by-character comparison on the string to check if the view needs invalidating.

Related Issues

N/A

Checklist

• I read and understood the contributing guide as well as the code of conduct
• The issues this PR addresses are related to each other
• My changes generate no new warnings
• My code builds and runs on my machine
• My changes are all related to the related issue above
• I documented my code

Screenshots