Get "Please enable cookies." when access from remote host.

# Bug report

Hi,

I'm working on deploying devdocs on no-internet-access internal for our team. We get "Please enable cookies." when someone access devdocs service from their own PC. But, the devdocs service works well when I access it from its hosted server.


I have to say this amazing project is very useful for me and thanks for your guys' contribution.

## Steps to reproduce

Just execute the command as README.
`git clone https://github.com/freeCodeCamp/devdocs.git && cd devdocs`
`docker build -t thibaut/devdocs .`
`docker run --name devdocs -d -p 9292:9292 thibaut/devdocs`

Then, access the service from localhost and a remote host.

You will get `"Please enable cookies."` when you access from remote host and can not save preferences.

You will not get `"Please enable cookies."` when you access via `localhost:9292`

从 README 中的 Docker 说明开始，复现 localhost:9292 与从远程主机访问之间的差异。然后跟踪该部署中涉及的 cookie 或偏好设置处理，接着验证远程用户不再看到“Please enable cookies.”，并且可以保存偏好设置。

由索引模型根据 Issue 内容生成。