As a plugin developer, I want to update my plugins' meta boxes to natively work with Gutenberg. For meta boxes that don't make sense as blocks (for example, a box with fields to populate open graph tags), I might want to add a box to the sidebar.

It would be helpful for theme and plugin developers to have an example of adding a meta box/pane, akin to the "Featured Image", "Excerpt", and "Discussion" boxes. It would be nice if there was an example of doing this for each available space (sidebar, below the editor, and if there's anywhere else).