[FEA] Improve datapipes API docs

[ktangsali]

Modulus Pull Request

Description

Improves API docs for Modulus datapipes.

Checklist

• [ ] I am familiar with the Contributing Guidelines.
• [ ] New or existing tests cover these changes.
• [ ] The documentation is up to date with these changes.
• [ ] The CHANGELOG.md is up to date with these changes.
• [ ] An issue is linked to this pull request.

Dependencies