Better walkthrough for documentation

[xcodian]

The current prompts used to guide the user through documenting methods (and other objects) feels rather uncomfortable to use, and could do with some work to enhance the UX.

• Possibly give the user the option to use their preferred terminal editor to edit the doc-string completely
  • Inspiration from how git does the git commit message editor
  • Allow the doc-string creation to be cancelled if the temporary file is not written
• Allow multi-line doc-strings to be manually created without relying on line-wrapping
• Clear up some of the language used to guide the user
• Better status indicators on each line, to show what you are currently documenting
• Showing the function definition to help documentation
  • eg. def func(number: int, float_param: float, misc) (without actual implementation)
• More meaningful color coding