DT-6455 Navigator introduction

[partisaani]

Proposed Changes

• Introduces the project with the new Design system
• Adds an introductory modal that's shown to user prior to their first journey using navigator

Pull Request Check List

• [ ] A reasonable set of unit tests is included
• [x] Console does not show new warnings/errors
• [x] Changes are documented or they are self explanatory
• [x] This pull request does not have any merge conflicts
• [x] All existing tests pass in CI build

Review

• Read and verify the code changes (I suggest you review commit-by-commit for additional context of specific changes)
• Test the functionality by running the UI locally with all popular browsers available in your platform
• Check that the implementation matches the design, when such one is defined in a Jira issue

TODO

• Meaningful unit tests