Add support for Tolino Shine 3

[Nepochal]

On Tolino Shine 3 devices Koreader uses TolinoRoot. This does not work for warmth.
I used the compatibility test and can confirm that it works with Tolino NTX. The same logic as implemented for the Tolino Vision 5 in #382 should work.

The device info is
Manufacturer: rakuten kobo inc.
Brand: rakutenkobo
Model: tolino
Device: ntx_6sl
Product: ntx_6sl
Hardware: e60k00
Platform: imx6

I would be able to give more information and test if someone implements and builds it.