feat: express list of contributors of an element(component, ...)

[prabhu]

We currently do not have a way to track the full list of all contributors for a component version. Since contributors could be different from authors, we need a better mechanism to track individual committers and authors using nested components or externalReferences (which could be a URL or BOM-Link).

[prabhu]

releaseNotes could also benefit from dedicated organizationContact attributes to track contributors, reviewers, and releasers.