Part 2 - Corpus Management more info - add row expansion

Design figma: https://www.figma.com/file/eSIeuIPKFwEDs4X9ky2O5E/Corpus-Registry?node-id=661%3A0

Add row expansion behind feature flag and show all corpus contents:

Unknowns

• Name of the field

Implementation Plan

• Mock out corpus files
• Leverage row details support as documented here https://bootstrap-vue.org/docs/components/table
• Render and iterate through the list of files
• Add Chevron icon with open and closed states
• Add unit tests