Typewriter mode

[Yukaii]

with dimmed non-active lines

• https://glamdevelopment.com/outlinely/learn/typewriter-mode
• https://ulysses.app/tutorials/typewriter-mode
• https://www.youtube.com/watch?v=XWcupcoGu68

[Yukaii]

Since we're using CodeMirror as our editor library, there're some implementations already

• https://oldj.net/blog/2019/06/30/codemirror-typewriter-mode
• https://discuss.codemirror.net/t/modified-typewriter-scrolling-addon-problem/452/2
• https://github.com/azu/codemirror-typewriter-scrolling