Extend `intersystems.servers` objects to contain optional `superServer` object

[gjsjohnmurray]

I am already doing this in an extension that uses the InterSystems Node.js Native API, which connects to the superserver port:

export interface ISuperServerSpec {
    host?: string;
    port: number;
}

export interface IServerSpec extends serverManager.IServerSpec {
    superServer?: ISuperServerSpec;
}

https://github.com/intersystems-community/vscode-iris-jupyter-server/blob/dbb4f99f2d245460292c45e1a45378e8c7ef69e1/src/server.ts#L6-L13