Add "help wanted" instructions to site

## Content

I would like the instructions on "how to open source" to include information on how to use the Code.gov "help wanted" labels so that GH issues can be displayed on the Code.gov site. Instructions for using these labels can be found on the ["code-gov" repo](https://github.com/GSA/code-gov/blob/master/HelpWanted.md).

## Page(s) Affected

https://www.code.mil/how-to-open-source.html

But maybe also https://www.code.mil/frequently-asked-questions.html ?

从 https://www.code.mil/how-to-open-source.html 中的说明开始，并比较 FAQ 页面，以确定是否两者都需要更新。阅读链接的 code-gov HelpWanted.md 指南，然后更新相关内容，以便贡献者了解如何使用标签，并确保页面准确说明 Code.gov 集成。

由索引模型根据 Issue 内容生成。