BO29 - Create a page to add a Sponsor

[gregoriopalama]

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

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

The breadcrumb should allow to navigate back to the list page for the single sponsorship level and for the sponsorship levels.
The name, the link and the logo are 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 sponsor has been added. Any error from the API should be notified using a red toast.

Depends on #193 and #186.