User preferences

[mbostock]

We should have user preferences for, at least as a minimum:

• Whether to trim trailing whitespace on commit
• Whether to automatically format code on commit (via Prettier)
• Configurable keyboard shortcuts?
• Whether to default to JavaScript or Markdown in new cells?

Related discussion in #35.

[yurivish]

I’m not sure if this is the kind of feedback you’re looking for here, so please feel free to ignore if it’s not helpful. But since it’s something that would be really valuable to me, I wanted to mention that I’d love if there were a setting to customize the prettier config, particularly the trailingComma setting.

[mbostock]

For prettier settings specifically I also imagine that Desktop should look in the current directory for a .prettierrc, since you might have different preferences for different notebooks.