Create Contributor ladder document for each sub-project

[yizha1]

Proposal of creating contributor ladder document by referring to the template https://github.com/cncf/project-template/blob/main/CONTRIBUTOR_LADDER.md

[toddysm]

Do we need that for each sub-project? Should we just have one for the whole project?

[yizha1]

Do we need that for each sub-project? Should we just have one for the whole project?

I think we need one for the whole project unless there is a special case for some sub-projects.