Bugfix: Block types do not show their descriptions

[iOvergaard]

Description

This maps the description property to the doc type model and displays it for block types.

Since the description field was added in umbraco/Umbraco-CMS#16503 it is now possible to fix this issue.

Fixes umbraco/Umbraco-CMS#16642

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Chore (minor updates related to the tooling or maintenance of the repository, does not impact compiled assets)

How to test?

1. Add a description to an element type and add that type to a block property editor
2. Add at least an addition block type (otherwise the block catalogue will not be shown)
3. Verify that the description is shown underneath the name

Screenshots (if appropriate)

Before

After

[loivsen]

LGTM 😊