feat: implement config option for the language switch

Feature

Summary

This MR provides the config option for the language toggle.

Does the result of the MR comply to our "definition of done"?

• Unit tests passed
• Code reviewed
• Acceptance criteria met
• Functional tests passed
• Non-Functional requirements met
• Product Owner accepts the User Story

Documentation

• I updated the README (if applicable)
• I provided my functions with appropriate documentation
• I adjusted other parts of the documentation (if applicable)

Tests

Are we able to test this new feature?

• Yes, everything can be done via unit tests.
• Yes, you can test by following these steps:

• checkout the branch: git checkout issue/make-language-switch-configurable and start your local env
• open index.template.html and set language-switch to false

=> expected: the switch doesn't show up

• No, it is not possible.

Changelog

• I added a statement to the CHANGELOG.

Related Tickets

Add all related issues and especially those to be closed.

Related

Closes

Logs and Screenshots

/cc Mathias Göbel, Frank Schneider, Michelle Weidling