Relative path in web interface

__Proposal:__
Use relative path in Influx v2 HTML interface to allow reverse proxy to a route like example.com/influx

__Current behavior:__
Unfortunately the main script fail to load because it need to be on the root path (i want it on /influx/)
I want to let example.com:8086 accessible as well for my telegraf nodes
https://prnt.sc/1030hrd

__Use case:__
It is not a priority at all and maybe not necessary but if it works and is easy for you to set up it could be a good thing.

No file or test is named in the issue. Start by locating how the web interface generates or serves the main script path, then reproduce it behind a /influx/ reverse-proxy route. Done means the HTML interface and its main script load correctly under that relative path while the existing root access remains available.

Written by the indexing model from the issue text.