[0.8.x] Fix base

[Madscientiste]

Fixes what i have mentionned in #197

when i set my vite.config with base: '/something/'
i expect also to have http://172.26.80.1:7894/something in my hotfile
...
If you specify a base path to vite, it means all the assets will be served from that base path. so if you have a base path of /somebasepath then all the assets will be served from http://localhost:3000/somebasepath/asset.js instead of http://localhost:3000/asset.js. This is useful if you want to serve vite from a subpath of your domain.

If i set a basepath and goes to the url without the base path it returns this:

The server is configured with a public base URL of /admin/ - 
did you mean to visit <a href="[/admin/@vite/client](view-source:http://localhost:7894/admin/@vite/client)">/admin/@vite/client</a> instead?

for some reason it doesn't stop my assets to load, but it breaks HMR

[jessarcher]

Sorry for the delay in getting to this one. It's a hard one to get my head around and make sure it doesn't introduce a breaking change, given all the different configurations we're trying to support and how base is set differently in dev mode vs build mode.

We recently merged #255, which hasn't been tagged yet but I think will allow you to solve your scenario. Feel free to re-open if it's not the case.

[timacdonald]

Related: #290