Element's iOS app needs to tell users when the Matrix server is not connecting.

#### Is your feature request related to a problem? Please describe.
Server's admin took his Matrix server down to do some works so I decided to see what happen if I try to use Element iOS app in my old iPhone 6 + (iOS v12.5.4). It didn't tell me that it couldn't connect. In Firefox web browser in my updated 64-bit W10 Pro PC, it told me it couldn't connect which was good messaging.

#### Describe the solution you'd like.
Element's iOS app should tell me/users that the server is not connecting. I know sending messages will say "Messages failed to send... [Retry]".

#### Describe alternatives you've considered.
It should be like the message when there's no Internet connection.

#### Additional context.
None.