Yes, this has been implemented. Such an annotation can be added as an HTML Label extension in the Extensions panel of the editor’s Viewer tab.
You can try it out in this scene: Contemporary Kitchen by Architecture Inspirations, and see how it was done in the accompanying video tutorial: INTERACTIVE Walkthrough on the WEB | Shapespark for Sketchup - YouTube.
Textual annotations are also possible, as described in this forum post: Room names in top and orbit views