Typing Animation

Create a Typing Animation. (Probably with JS?)

The issue is to create a typing animation, likely for text in the DOM. Look at existing utility functions in the repository to understand the codebase style. Research JavaScript methods for manipulating text content and timing (like setInterval). A 'done' state would be a reusable function that animates typing text into a specified DOM element.

索引モデルが issue の本文から書いたものです。