Updated contributing guide

See merge request docs/docs.beagleboard.io!65

```shell-session
$ source ./venv-build-env.sh
$ cd projects/librobotcontrol/docs
$ doxygen
$ cd ../../..
$ sphinx-build -M html . public
```

Previously added instruction prevented the play from booting, this change fixes that.

Fix greybus host docs for beagleplay

See merge request docs/docs.beagleboard.io!64

Signed-off-by: Ayush Singh <ayushdevel1325@gmail.com>

My Main to Staging of Main/relay.rst and 02sensors.rst

See merge request docs/docs.beagleboard.io!50

Updated Instructions up to Flashing CC13

See merge request docs/docs.beagleboard.io!63