Allow connecting to "open" (no password) network

[brentru]

Similar to adafruit/Adafruit_IO_Arduino#156. Once implemented here, issue can be fixed in AIO_Arduino as well.

[brentru]

+1 in https://forums.adafruit.com/viewtopic.php?p=947275#p947275

[coredatascientist]

I'd be interested in this feature as when the password is left blank it currently results in a red neopixel.

[brentru]

We can do WiFi ENT via espressif/arduino-esp32#6398