Mac app

[chrissearle]

We should be able to build a mac app.

Some dependencies need upgrading or alternatives first:

• AlamoFire - OK
• WaterfallGrid - OK
• SwiftUIRefresh - UIKit only - to be removed when iOS15 and above - see Remove SwiftUIRefresh dependency #38
• RemoteImage - not sure - can't see any UIKit specific stuff - needs testing