Provide contextual help when users are trying (but failing) to connect to a courier

[gnarea]

This is what users see today on Android and desktop when they're not connected to the Internet or a courier:

It'd be good to offer some help in case they're trying to connect to a courier, but aren't managing to do so. For example, we could display a button that says something like "I can't connect to a courier", which opens a screen that shows information like:

• How to find a courier. It'd be great to provide concrete, region-specific info in addition to the general info (see Publish country- and region-specific recommendations for couriers and end users #24).
• If they're in close proximity with a courier but failing to connect, offer solutions to common problems (e.g., WiFi signal out of range, wrong WiFi password).
• WiFi status: Whether the WiFi is on, and if so, show the name of the current network (if any).