Feat/us143 implement high contrast mode

[KoenvanMeijeren]

Description of your PR.

Definition of Done

Designs

• The new changes are documented in the functional & technical designs.

Development and Testing

• The new functionality has been tested by at least one of the other team members, and all tests are successful.
• The test results are added to the test report documentation.
• The implemented User Story complies with its acceptance criteria.
• The new functionality is reviewed by at least two other team members.
• The new functionality is compliant with the rules of chapter 6.2 Quality in the project plan.

Unit, component & E2E testing

• Unit tests are written for the general purpose code, e.g. libraries or utility methods
• Component tests are written for standalone components, e.g. Buttons, Alerts
• E2E tests are written for pages, e.g. the home page
• E2E tests: Components use the "testID" attribute for testing

App testing

Build the app and test it on your phone.
This is important, because we've on a regular basis issues with the app on mobile phones, but not with the website.

• Everything works as expected
• No weird usability bugs
• No errors or warnings during the tests

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Please ensure that all the checkboxes are ticked before submitting the pull request.