Issue Type: Feature Request

Here's what I have tried using this as a reference:

"myextension.myProperty": {
    "type": "string",
    "default": "",
    "markdownDescription": "This is my property description and I want to link this [command](command:editor.action.addCommentLine)!"
}

In the settings page, "command" doesn't show up as a link, just plain text. It would be nice if command links were supported like regular URL links.

VS Code version: Code 1.32.3 (a3db5be, 2019-03-14T22:46:48.547Z)
OS version: Darwin x64 18.2.0