BO25 - Create a page to add a Sponsorship level

[gregoriopalama]

Create a page that will be opened by clicking on the "add" button in the sponsorship levels' list page.

The page should be allowed to Devfest Organizers only and should allow the input of the informations for the level, as shown below:

The breadcrumb should allow to navigate back to the list page.
The name is strictly required.
The "Cancel" button will navigate back to the list, the "Save" button will perform the call to the Sponsorship API and navigate back to the list, showing a toast that will confirm that the level has been added. Any error from the API should be notified using a red toast.

Depends on #182 and #189.