add citation information

还没有人认领这个 Issue。

I'd like to cite jupyter-matplotlib in something I'm working on. What is the preferred citation information for this repository? If I use Zotero to scrape the metadata this is what I get:

```
@misc{jupyter-matplotlib_2019,
title = {jupyter-matplotlib},
copyright = {BSD-3-Clause},
url = {https://github.com/matplotlib/jupyter-matplotlib},
abstract = {Matplotlib Jupyter Extension. Contribute to matplotlib/jupyter-matplotlib development by creating an account on GitHub.},
urldate = {2019-11-19},
publisher = {{Matplotlib Developers}},
month = nov,
year = {2019},
note = {original-date: 2016-07-21T14:38:56Z},
}
```

however, I'm not sure of how authorship should be determined? I could list all 13 contributors of this repository, or it could be "Matplotlib Developers", or something else? What would be best here?

I'm happy to contribute this information back into the repo in the readme or a citation file if you'd like too.

首先检查仓库 README 和任何现有的引用元数据。根据仓库信息确定首选的作者署名和引用格式，然后将其记录在 README 或引用文件中，以便用户能够以一致的方式引用 ipympl。

由索引模型根据 Issue 内容生成。