I know that ace editor[1] has key biding for vim. The chrome plugin SurfingKeys[2] use it internally.

[1] https://ace.c9.io/

[2] https://github.com/brookhong/Surfingkeys

Actually I've always wanted Microsoft Office and Outlook editors to behave like vim

since this site doesn't let you experiment, i'd guess they didn't actually emulate vim. it's little more than a slide deck triggered by specific keypresses.

Closest thing I can think of is CodeMirror: https://codemirror.net/demo/vim.html