Add a volkswagen CI badge

Description

Adds a Volkswagen CI badge to the readme.

Changes

None.

Additions

Adds a Volkswagen CI badge.

Test and Review

To be filled in by the reviewers

• There are no unnecessary files present in the MR

• The continuous integration has no problems with the MR

• The MR is filled in as requested (including labels, milestones, and reviewers)

• The documentation is up-to-date