Document the existence of ExpressLRS Telemetry Widget

I absolutely love this widget and use it with every EdgeTX model setup. However, I believe it lacks a bit of visibility, which might cause new users to miss out on its usefulness. It could be a good idea to suggest or promote the use of this widget during the first-time setup or in another suitable place.

Link: https://github.com/ExpressLRS/ElrsTelemWidget