Alert Linux users when Ledger devices won't connect

[mhluongo]

On Linux, Taho can't connect to Ledger devices without adding udev rules.

When the rules aren't set, the Ledger connection fails, without any clear error message. That's a shame, since the Ledger connection experience elsewhere is one of the best I've used.

Here's what's logged in the background page when the issue comes up. We should be able to catch this + check the OS, then show a reasonable error with a link to instructions.

logger.ts:208 Treating Ledger as having disconnected due to a connection error: SecurityError: Failed to execute 'open' on 'USBDevice': Access denied.