docs: document support for 802.15.4 hat
docs: document support for 802.15.4 hat

Signed-off-by: Anton Gerasimov <4a32388baf18e0e27356df90b349bc440aec3b53@gmail.com>

agherzan/meta-raspberrypi,schnitzeltony/meta-raspberrypi,agherzan/meta-raspberrypi,agherzan/meta-raspberrypi,kraj/meta-raspberrypi,schnitzeltony/meta-raspberrypi,leon-anavi/meta-raspberrypi,agherzan/meta-raspberrypi,leon-anavi/meta-raspberrypi,kraj/meta-raspberrypi,kraj/meta-raspberrypi,leon-anavi/meta-raspberrypi,agherzan/meta-raspberrypi,agherzan/meta-raspberrypi,schnitzeltony/meta-raspberrypi