Add Baseurl to allow subfolder usage

[sepulzera]

Reported by CMclarty.

Would it be possible to add a BaseUrl option to the configuration options available? i.e

BaseUrl=/openeats/

I'm not a programmer, but I did a bit of google-fu and believe the process is relatively straightforward for React apps, which I believe the front-end is built on.

Argument
Many of the target audience for OpenEats will have multiple services running on a server. Adding a Baseurl allows one proxy server to simply serve all services from a single domain via subdirectories, keeping cost and complexity down and allowing one SSL config/Auth policy to cover all services. I believe the work involved fits within the overall goals of the project :)

Thanks again, and please let me know if i've missed something.