Allow setup to continue past mqtt if network/wifi is disabled (#5754)

esphome/components/network/util.h

@@ -8,6 +8,8 @@ namespace network {
 
 /// Return whether the node is connected to the network (through wifi, eth, ...)
 bool is_connected();
+/// Return whether the network is disabled (only wifi for now)
+bool is_disabled();
 /// Get the active network hostname
 std::string get_use_address();
 IPAddress get_ip_address();