…oogleapis#2547)

The \ue907 character is intentional Google Docs API behavior, not a bug.
This addresses user confusion by:

- Adding comprehensive documentation explaining the Unicode placeholder behavior
- Providing a working example showing how to extract actual date/chip data
- Demonstrating best practices for working with richLink properties
- Clarifying that this is API design, not client library issue

The Google Docs API intentionally replaces non-text elements (smart chips, dates,
people, etc.) with Unicode Private Use Area character U+E907 in TextRun.content,
as documented in the API specification. The actual data is available in
richLinkProperties within the same document elements.

This is an educational contribution to help developers understand expected
API behavior and implement proper workarounds.