Coder plugin: Add example of customizing Workspaces Card

I know it is possible to customize the CoderWorkspacesCard to include or hide certain components. Could we provide an example of this, for example, with adding custom text below the table? I think this would be an excellent place to showcase that the "Or open in Dev Containers" can be added.

Start by locating the CoderWorkspacesCard entry point and any existing plugin examples. Add an example showing how to customize the card with text below the table and how to include “Or open in Dev Containers”; done means the customization is documented in a runnable or discoverable example.

Written by the indexing model from the issue text.