Updated serialport version

This release updates serialport dependency to 9.2.8

What's Changed

• update to serialport@9.2.8 by @abythell in #9

New Contributors

• @abythell made their first contribution in #9

Thanks @abythell

Update to use latest serialport and xbee-api libraries

Updating README.md

Adds credits

Initial Release

The very first release of node-red-contrib-xbee