StreamField blocks previews

[thibaudcolas]

Summary

Block descriptions and previews will support content editors in making more informed choices when selecting blocks, speeding up the creation of new content.

Intended Outcome

• Developers will be able to add StreamField block descriptions, similar to page_description, but for block types.
• They will also be able to add StreamField block preview screenshots.
• When added, this information will appear within the block chooser UI for CMS users.

More information

See: StreamField block type descriptions and image previews in block chooser #11997.

[rvoorhorst]

I would love to see this in Wagtail! Currently it is very difficult to see the difference between the different content blocks when they are all collapsed.