[Frontend] - Interact with user's workflow from the extension tab

[garciagenrique]

Last functionality of the frontend - set up for the 3rd (or later) iteration.

Let's start simple by

• [x] Showing the 4 sub tabs that a workflow shows: Engine logs, Job logs, Workspace, and Specification.
• [x] Implement a functionality to allow downloading a single file and/or all the files of a REANA workflow into the Jupyter lab local storage