feat: 马丽 learns of connection loss when fetching unavailable assets

[toshify]

马丽 looses connectivity during the first time she opens the app after she can see the splash screen. She sees a graphic indicating connection loss. She hears a relevant audio instruction.

马丽 opens the app again and sees the home screen. She looses connectivity, then taps a lesson. She sees a graphic indicating connection loss. She hears a relevant audio instruction. She taps a button to return to the home screen.

Requirements

• Provides a graphic to indicate connection loss
  • unplugged cable might wrongfully indicate to plug in a charger, but could also be correctly interpreted. A wifi icon flashing with a ! or crossed out might also communicate.
• Provides audio instructions about the issue and how to proceed
  • TTS or recorded audio
• Loads required assets early in splash screen loading queue to immediately handle connection loss
• Adds timers or otherwise rely on events to handle connection loss during splash loading.
• Adds timers or otherwise rely on events to handle connection loss during lesson loading.