kubernetes/kubernetes-docs-* repos need to be added to sigs.yaml

[spiffxp]

ref: #2464

Ownership of the code each of these repos needs to ultimately fall to a single sig. In this case it seems like it should be sig-docs. Adding them to sigs.yaml will help us track this.

I'm not sure which makes more sense, one i18n subproject that is responsible for all these repos, or a subproject for each language

This isn't an attempt to voluntold repos to a sig, just a guess. If I'm wrong, help me figure out which SIG should own these.

/area github-management
/sig docs
@kubernetes/sig-docs-maintainers
/assign @zacharysarah @chenopis @jaredbhatti
as sig-docs chairs