WP 5.0+ Gutenberg integration

[johnwatkins0]

Is your enhancement related to a problem? Please describe.

In WordPress 5.0+, the Vue-based metabox created by the library doesn't look great:

Even when forced into the sidebar, it sticks out visually because it doesn't use core blocks:

Describe the solution you'd like

New JS for Gutenberg using React and core packages, creating either a metabox or a plugin sidebar.

Additional context

Using this library in a client project that needs post-to-post relationships.