Add support for vertical rulers/guides

[cosinami]

This is a feature of the Monaco Editor that I think would be a welcome addition to Code App.

Currently, within VS Code, vertical rulers are added/modified through the following settings.json property:

"editor.rulers": [
     80,    // A vertical line at column 80.
     120   // A vertical line at column 120.
]

For Monaco, to my knowledge, rulers is managed through its EditorOptions property.

[bummoblizard]

Actually we should add support for settings.json.

Reference: https://code.visualstudio.com/docs/getstarted/settings#_workspace-settingsjson-location