Update contributing docs, sign CLA after pull request.
Update contributing docs, sign CLA after pull request.

mgiannikouris/vi-firmware,ene-ilies/vi-firmware,openxc/vi-firmware,ene-ilies/vi-firmware,mgiannikouris/vi-firmware,mgiannikouris/vi-firmware,openxc/vi-firmware,ene-ilies/vi-firmware,mgiannikouris/vi-firmware,openxc/vi-firmware,ene-ilies/vi-firmware,openxc/vi-firmware