Develop: Chatbot link from all pages

[mdconatser]

As a user, I want to be able to access the chatbot functionality from any page that I am on, not just the homepage.

See mockups: https://xd.adobe.com/view/db7cd80e-542d-495d-8909-01d4b2607dbe-8e2f/screen/82e4c1df-4679-457b-9096-2d932ceab552

Acceptance Criteria

• Chatbot user interface can be opened from any page
• Document any relevant content in the Programmer guide (draft thoughts of usage and importantly the "Why")
• Updates SRS and STP (and other docs if necessary)
• Add/Update relevant unit tests