Add missing documentation

[stv0g]

• [ ] Node-types
  • [x] can
  • [x] comedi
  • [x] ethercat
  • [ ] fpga
  • [x] iec61850-9-2
  • [ ] iec61850-8-1
  • [x] rtp
  • [x] signal_v2
  • [x] stats-node
  • [x] test-rtt

[stv0g]

marked the checklist item can as completed

[stv0g]

marked the checklist item comedi as completed

[stv0g]

marked the checklist item ethercat as completed

[stv0g]

marked the checklist item iec61850-9-2 as completed

[stv0g]

marked the checklist item rtp as completed

[stv0g]

marked the checklist item signal_v2 as completed

[stv0g]

marked the checklist item stats-node as completed

[stv0g]

marked the checklist item test-rtt as completed

[stv0g]

Done