Portenta Breakout datasheet: Add ethernet jumper pads info (#206)

* Datasheet: Add ethernet solder jumpers section

* Datasheet: Update related products

* Apply suggestions from code review

Co-authored-by: Sebastian Romero <s.romero@arduino.cc>

* Add image descriptions

* Update changelog

Co-authored-by: Sebastian Romero <s.romero@arduino.cc>

Author: marqdevx