Add example demonstrating how to configure a static IPv4 address in lieu of DHCP

[ssnover]

I had to do quite a bit of spelunking in the docs to figure this out and I think this is a fairly common use case (esp-wifi has an example like this).

One question I had was why the API for swapping the network interface configs needs to swap both the STA and AP configs at once when many are not necessarily using both? It'd help clean up this example if that were possible and the code of anyone who isn't running an ESP device as both an AP and STA device.

Testing

I tested this on an ESP32C3 on the ESP32-C3-MINI-1 dev board.

[ivmarkov]

One question I had was why the API for swapping the network interface configs needs to swap both the STA and AP configs at once when many are not necessarily using both? It'd help clean up this example if that were possible and the code of anyone who isn't running an ESP device as both an AP and STA device.

Pure laziness on my side. I don't think there's anything wrong with exposing - e.g. - swap_netif_sta and swap_netif_ap - in addition to the existing swap_netif method.