Add support for Xtensa LX7

[Jesse Braham]

The ESP32-S2 and ESP32-S3 are based on the Xtensa LX7 processor. I have opened #12 which adds "support" for this device, however there should probably be some conversation on how we want to handle this moving forwards. Since the Xtensa processors are configurable, there is not necessarily a consistent set of available features.

[Jesse Braham]

With #15 merged, is there anything actionable left here or can this issue be closed? @MabezDev @bjoernQ

[Björn Quentin]

I don't think anything is left to do here - as far as I can see everything else to support ESP32-S2 / ESP32-S3 is to be done in xtensa-lx-rt

If that turns out to be wrong, we can still create a new issue here

[Jesse Braham]

Great, that's what I thought as well. Thanks!