Add note about first PR in README_CN.md

[ForYiver]

Which issue or RFC does this PR close?

Closes #.

Rationale for this change

What changes are included in this PR?

Are there any user-facing changes?

How was this change tested?

AI usage statement

[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}

[hidb4ai]

Thank you for your interest in contributing to PowerContext. This PR does not address a specific problem or meet the project's contribution requirements, so it cannot be accepted and has been closed.

We welcome your participation and encourage you to submit a new PR that addresses a clearly defined issue and follows our contribution guidelines.