Enhance settings schema to provide autocompletion, color picker

[baincd]

I think it would be great to add JSON schema to the more complex settings. Doing this will provide autocompletion, validation, default values, example or enum values, and color pickers for colors. Since these settings cannot be edited through the settings UI, adding this additional metadata is extremely helpful. It allows users to be able to modify settings quickly in settings.json without having to lookup or refer to the documentation.

• Descriptions are based on the text in the README.
• Examples and enums come either from the README or from documentation for the CSS style (w3schools and/or MDN)

Note: for the icon property examples, the codicon example in the autocompletion shows the actual icon rather than the value. I could not find a workaround to that.

[Gruntfuggly]

Hi - I am already in the process of doing this. I'll have a look at your changes too.

[depascalis]

Related to issue #512