## Cause
It broke because lack of awareness that we can't use our components in preview mode. For some reason, we don't have redux access in SimpleMDE's preview mode.
## Change
- Restore the stub for iframes
- Fix preview for images, and apply a similar styling as in Posts.
Co-authored-by: jessopb <36554050+jessopb@users.noreply.github.com>
## Issue
4644: Markdown Preview breaks when <iframe> is present
Error: "Invariant violation: could not find 'store' ..."
## Change
Until we figure out a way to pass the store to the SimpleMDE preview formatter, just replace the embed with a stub region.
