Feature request: Let user customize indentation settings

[tom]

Update!

"prettier" code formatting

Update: Prettier-powered autoformatting is now available to folks to test. Open your browser console localStorage.tryPrettier = true Evaluate cells with Shift-Enter or by clicking the button, and they’ll be formatted. Let us know what you think, and if you run into any issues using this beta feature! you can turn it off again by running localStorage.removeItem('tryPrettier'). [prettier]