Can't send messages on local network without internet connectivity.

Even if it can reach the homeserver, Element Android can't send messages without connectivity to the public internet.

After discussing with @BillCarsonFr we think that the WorkManager for sending messages might not be triggering because the networking constraint [CONNECTED](https://developer.android.com/reference/androidx/work/NetworkType) is not being met (if the device can't reach google.com, perhaps).

There are plans under discussion for moving message-sending out of a backgroundable work manager (related to performance rather than this issue).