Update sponsors list

[vtsatskin]

We are using an outdated list

[srcreigh]

if you have access to forge, you can update the url given at hackthenorth.firebaseio.com/mobile/sponsors to an arbitrary image which will be loaded on both platforms

[srcreigh]

otherwise, can you first work out what the sponsors should be, and then do what I have previously instructed? thanks! lmk if you have questions