add documentation about DCO

[reginapizza]

What type of PR is this?

/kind documentation

What does this PR do / why we need it: Now that DCO checks are enabled, this will add documentation about it as requested by Red Hat Legal team.

Which issue(s) this PR fixes: https://issues.redhat.com/browse/GITOPS-2122

[reginapizza]

/retest

[reginapizza]

@wtam2018 Red Hat Legal states the following in their FAQ:

If your project uses the CoreOS method, add the following text to a CONTRIBUTING.md file in the root directory of your project repository:

Certificate of Origin

By contributing to this project you agree to the Developer Certificate of Origin (DCO). This document was created by the Linux Kernel community and is a simple statement that you, as a contributor, have the legal right to make the contribution. See the DCO file for details.

and

11. Can we modify or customize the DCO certification text? No (unless you get approval from Red Hat Legal). The Linux kernel project has requested that modified DCOs not be used so that the community can standardize on one text.

[wtam2018]

I thought you were granting copyright our software to 1 Letterman Drive Suite D4700 San Francisco, CA, 94129 when I first looked at it. It was actually the copyright of the DCO. I think you can just use this link. https://developercertificate.org/

[reginapizza]

haha no worries, that wouldn't be good! Also in the FAQ they state:

While there are various ways of doing this, we currently recommend the following approach. First, add a file to the root directory of your project repository containing just the text of version 1.1 of the DCO (example: https://github.com/metal3-io/metal3-docs/blob/master/DCO).

I took the text here from the example given above. The only different between the text at https://developercertificate.org/ and here is the additional address. If you really don't think it should be there, let me know and I'll change it but otherwise I think it's a minor difference.

[wtam2018]

/lgtm /approve

[openshift-ci[bot]]

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