[Design Toolbox] Use translated strings for demos and illustrations

[paulinea]

Prerequisites

• I have searched the backlog for duplicate or closed issues.

Description

Demos content should use translated strings. As an example, button label should be translated when in Arabic or French.
To resume, we have:

• non-translated strings for API parameters (string keys suffix is _tech)
• translated strings for demo content and components illustrations (string keys suffix is _label)