docs: add CoC notice and Security Policy

Signed-off-by: WaitSpring <me@waitspring.com>

CODE_OF_CONDUCT.md

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+# About _Common Program of Qiuwen Baike_ 关于《求闻百科共同纲领》
+
+The development of this software is subject to the _Common Program of Qiuwen Baike_, which is a constitutional document of _Qiuwen Baike_ and its community and plays the role similar to code-of-conducts in other open-source communities.
+
+本软件之开发遵循《求闻百科共同纲领》，该文件为求闻百科纲领性文件，起到类似其他开源社区中“行为准则”的作用。
+
+You can read the _Common Program_ at <https://qwbk.org/c/31162>.
+
+您可以在下列网址查阅《共同纲领》：<https://qwbk.org/c/31162>。

SECURITY.md

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+# _Reporting a Vulnerability_ 反馈安全问题
+
+Should you believe that there were vulnerabilities or problems,
+please report them to `adjcom at volunteers.qiuwen.org`.
+
+若您确信求闻百科小工具存在安全问题，请将相关问题通过邮件发送至`adjcom at volunteers.qiuwen.org`。