Gets or sets the renderer that draws the tiles it accepts outside the viewer's thread (a browser Web Worker), or
null (the default) to draw every tile with BackendFactory's backends. The session that opens
with these options owns it and disposes it when it closes, so set it on options used for one session.
public IRemoteTileRenderer? RemoteRenderer { get; set; }
Spec #33 viewer capability 1 (#357).