Make use of both detail and documentation fields

[meganrogge]

When we have a command that has both a description and a path, we should show those both similar to what the editor does.

We'd need to add documentation to our API.

vscode/src/vscode-dts/vscode.d.ts

Lines 4919 to 4927 in ff59377

	* A human-readable string with additional information
	* about this item, like type or symbol information.
	*/
	detail?: string;
	/**
	* A human-readable string that represents a doc-comment.
	*/
	documentation?: string | MarkdownString;

[meganrogge]

cc @Tyriar