Add drop down into nav bar on Rapid Router to introduce translater

[lauracumming]

Task Description

Add a drop down into the nav bar in Rapid Router in order to add the option to translate the blocks.

Acceptance Criteria

• [ ] drop down added to Nav bar
• [ ] set the user's preferred language as the default language

Analytics Requirements

• [ ] Create tag in tag manager to track clicks

Something like this would be great: https://www.figma.com/file/6802Amjc4GKRdqzm26ozaw/While-Loop-levels?type=design&node-id=114%3A638&mode=design&t=S49ZCz1J60y1ePHG-1

[lauracumming]

@faucomte97 @SKairinos please groom for @evemartin