Implement groups membership sidebar for the navigation menu

While the new designs are being finalized, we can started on our new epic

We'll be using this mock as a starting point. We're going to have to fit each section of the site into the existing format the best we can and we'll be fixing each section as they go.

git lab mocks

https://design.minds.com/hosted/web/michael/front%232148-navigation/#artboard0

responsive

https://design.minds.com/hosted/web/michael/front%232148-navigation/#artboard6

https://design.minds.com/hosted/web/michael/front%232148-navigation/#artboard7

Opened menu

https://design.minds.com/hosted/web/michael/front%232148-navigation/#artboard8

• Implement a "redesign" feature flag that will control how we load the css / new site designs
• Display the list of groups a user is subscribed to on the left hand side
• End to end tests to make sure the groups navigation works