docs(blind): add ux description

[linstedt]

Pull request checklist

Please check if your PR fulfills the following requirements:

• Tests for the changes have been added (for bug fixes / features)
• Docs have been reviewed and added / updated if needed (for bug fixes / features)
• Build (yarn build) was run locally and any changes were pushed
• Unit tests (yarn test) were run locally and passed
• Visual Regression Tests (yarn visual-regression) were run locally and passed
• Linting (npm lint) was run locally and passed

Pull request type

Please check the type of change your PR introduces:

• Bug fix
• Feature
• Refactoring (no functional changes, no API changes)
• Build related changes
• Documentation content changes
• Other (please describe):

What is the new behavior?

• added UX description and illustrations for control Blind

Other information

Review required:
[ ] accuracy and comprehensiveness of description
[ ] new picture location for illustrations - location and references acceptable?
[ ] should we report sizes/ spacing ? If so, how (unit)?
[ ] Code preview section untouched except headlines, a more condensed preview would be helpful for more complex controls

General question: Which ones of the PR requirements above apply to documentation extensions?

[danielleroux]

lgtm