thanks!

i simplified it to this one-liner:
```
ACTION=="add|change", SUBSYSTEM=="usb|tty|hidraw", ATTRS{idVendor}=="16c0", ATTRS{idProduct}=="27dd", MODE="660", GROUP="plugdev", TAG+="uaccess"
```

is it ok if i put that in the `postcard-rpc` docs rather than your version with the label? (i just learnt that udev rules support `GOTO`... but i really don't like `GOTO` in any language 😆)