message: add pinout table
diff: @@ -6,6 +6,9 @@ The ODrive can be controlled over various ports and protocols.
  [TODO: include a picture that shows all interfaces with the supported protocols]
  +
  +
  +
  ### Table of contents
  <!-- MarkdownTOC depth=2 autolink=true bracket=round -->
  @@ -21,6 +24,21 @@ The ODrive can be controlled over various ports and protocols.
  <!-- /MarkdownTOC -->
  +## Pinout
  +
  +| GPIO | primary | step/dir | other |
  +|-----------|-----------|------------|-------------------------|
  +| GPIO1 | UART TX | Axis0 Step | Analog input, PWM input |
  +| GPIO2 | UART RX | Axis0 Dir | Analog input, PWM input |
  +| GPIO3 | I2C Addr0 | Axis1 Step | Analog input, PWM input |
  +| GPIO4 | I2C Addr1 | Axis1 Dir | Analog input, PWM input |
  +| GPIO5 | I2C Addr2 | | |
  +| GPIO6 (*) | | | |
  +| GPIO7 (*) | | | |
  +| GPIO8 (*) | | | |
  +
  +(*) available on ODrive v3.5 only
  +
  ## Ports
  ### USB
  