TunnelsManager: Ask to check Internet connectivity in error alert

Signed-off-by: Roopesh Chander <roop@roopc.net>

WireGuard/WireGuard/Tunnel/TunnelsManager.swift

@@ -42,7 +42,7 @@ enum TunnelsManagerActivationAttemptError: WireGuardAppError {
 enum TunnelsManagerActivationError: WireGuardAppError {
     case activationFailed
     func alertText() -> AlertText {
-        return ("Activation failure", "The tunnel could not be activated")
+        return ("Activation failure", "The tunnel could not be activated. Please ensure you are connected to the Internet.")
     }
 }