👌 IMPROVE: Give a better indication of what the work chain is doing as it is running

[mbercx]

Is your feature request related to a problem? Please describe.

As noted by @mkotiuga in #102, the title of the steps in the outline is perhaps not the most user-friendly information to present for the Status step. It's not very clear what exactly the work chain is doing, especially when the user doesn't expand the work chain (because e.g. the "+" button isn't clear).

Describe the solution you'd like

It might be good to add a spinner here with some information on what's going on (e.g. the relaxation/band structure calculation etc).

Additional context

Loosely related to #68