Add support for Teltonika RUT 200/240/241

Hi!

I use a few Teltonika RUT 240/241 and now also RUT 200. They use a fork of OpenWrt ("RUTOS") and they are fully open source but unfortunately they are way behind recent OpenWrt development so I'd like to have true OpenWrt support instead.

I notice that there are a number of other similar Teltonika routers supported and a few years ago there was development ongoing to support RUT 240. The old thread is dead.

You can read about RUT 200 here: https://teltonika-networks.com/products/routers/rut200

The old RUT 240 thread is here: https://forum.openwrt.org/t/getting-rut240-to-work/46868

Teltonikas SDK is here: https://wiki.teltonika-networks.com/view/Software_Development_Kit

Is there anyone working on any of these devices?

I've been using OpenWrt regularly since 2007 (White Russian/0.9) but I have no porting experience. I can provide hardware to anyone interested in helping me with this.