feat: add MessageFeedback + UserMessage (#10086)
* fix: rebase commits + add stories
* feat: migrate MessageFeedback and UserMessage components to s2-ai package
* Apply suggestions from code review
Co-authored-by: Yihui Liao <44729383+yihuiliao@users.noreply.github.com>
* add missing file
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Co-authored-by: Yihui Liao <44729383+yihuiliao@users.noreply.github.com>