[docs] Add Tong Wu and Zhiyuan He as code owners

[shiyu1994]

As mentioned in #4677, add Tong Wu @tongwu-msft and Zhiyuan He @hzy46 as code owners.

[jameslamb]

Great! Welcome @tongwu-msft and @hzy46 . Let me know if you have any questions about the development processes here.

@shiyu1994 can invite you to the maintainer Slack, where we occasionally talk privately about sensitive topics related to this project.

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I've added the doc label here.

In case you weren't aware, and for the benefit of new contributors, let me explain why. Every PR we merge becomes one item in the release notes, and every PR must have a label so that it's categorized correctly on the release notes.

See https://github.com/microsoft/LightGBM/blob/717f037c3aa59b55145e0896cfbf85f918f3eb88/.github/release-drafter.yml for the mapping of labels to release notes sections.

[github-actions]

This pull request has been automatically locked since there has not been any recent activity since it was closed. To start a new related discussion, open a new issue at https://github.com/microsoft/LightGBM/issues including a reference to this.