Need the file of 'CONTRIBUTING.md'

[lubinsz]

Hi,
Our legal department need to check the policy for contribution.
But I can't find the file of 'CONTRIBUTING.md'

For your reference:
'CONTRIBUTING.md' in runc,
https://github.com/opencontainers/runc/blob/master/CONTRIBUTING.md

[jameskellynet]

See the part about the CLA here: https://tungstenfabric.github.io/website/