Replace CodeMirror with Microsoft Monaco

[David-Carty]

Please delete.

[mrdoob]

Sorry, I was on holidays last week.

[mrdoob]

Original request:

Frames.js looks absolutely bursting at the seams with potential.
But CodeMirror, really?
I was a huge advocate of CodeMirror when my Grandfather was still working the fields, then Monaco Editor came along.
No need for TypeScript.
The NPM exposes the runtimes and they can be just dropped in, just like CodeMirror.
But you're the boss, for sure.

[David-Carty]

Initially, I did not realise when frame.js was written, clearly, CodeMirror was the best choice at the time. It now seems trivial to have even raised this issue. Feel free to close. D.