Preview mode in Layout Builder doesn't show anything

Problem/Motivation

When a salesforce_mfw block instance is added via Layout builder, when the Preview option is selected,
there is no indication that the block is there. See attached screenshots.

Steps to reproduce

*Assumes site is configured to work with layout builder and is enabled*
1) Add a salesforce_mfw block via layout builder
2) Enable `Preview Content` under `Display Options`
3) No indication that the block is there.

Proposed resolution

Add some type of preview text when in preview.