Add documentation on how to do good OSS documentation

## Feature

We would like to have better documentation on how to create good open source software documentation as guidance for Department organizations wishing to open source things. This should include things like relevant sections of a "contributing" doc (not just a link to an example), how to write and review PRs, good commit messages, how to write a good GH issue, etc.

## Page(s) Affected

This could go on https://www.code.mil/how-to-open-source.html ("How to Open Source"), but it could live on it's own page, linked a couple of places.

首先阅读现有的 https://www.code.mil/how-to-open-source.html 页面，并审查此 Issue 中请求的指导领域：贡献文档、pull requests、commit 消息和 GitHub issues。指导内容完成撰写，放置在该页面或一个已链接的新页面上，并从相关位置链接到它，即视为完成。

由索引模型根据 Issue 内容生成。