Resolve "Show a "prototype" banner so it's clear it's not yet in production"

Description

Adds a "PROTOTYPE" banner so we know demos are not official geoportals

Job done

A prototype web componenet

Definition of Done

For the Developer:

• Code compiles and conforms to defined coding standards (eslint, tsc, prettier).
• If necessary (at the developer's discretion), unit tests have been added for critical parts.
• All unittests run without error.
• Sonar-Scan returns no new issues or security hotspots.
• Documentation has been updated where necessary (see documentation repository).
• Merge-Request contains a few explanations of what was done.
• A Reviewer has been assigned to the Merge-Request.

For the Reviewer:

• New code was reviewed.
• If comments could be added on unclear code, the developer has been informed.
• If unitests could be added in certain places, the developer has been informed.
• Merge-Request was merged on main branch.
• All pipelines work.
• The bugfix was tested on demo environment.
• Application performance has not been degraded by the modifications.

Authors

Closes #218 (closed)