keyWindow deprecation warning during build

[Flowm]

Nothing critical right now, just something to fix for future releases:

meteocool/ios/meteocool/lib/LocationUpdater.swift:138:63: 'keyWindow' was deprecated in iOS 13.0: Should not be used for applications that support multiple scenes as it returns a key window across all connected scenes

[v4lli]

Thanks for the report. :) Will try to fix this in soon, tracking in #84