Improve README options list with clear default values.

[Floriferous]

Hi there,

Going through the README, I arrived at the options section (https://github.com/sagemathinc/http-proxy-3?tab=readme-ov-file#options), and noticed that the structure is slightly inconsistent. The default value for each option is not always present, so it's not easy to understand what the default/customized behavior is? Maybe a table with Name/Description/Allowed values/Default would be better?