[Feature request] Client config

[Mister-Hope]

Clear and concise description of the problem

Provide client config file for theme and plugins, so that user can modify client-only options to get an HMR instead of a server restart.

Suggested solution

See https://github.com/vuepress/vuepress-next/issues/914#issuecomment-1143325774

Alternative

No response

Additional context

No response

[meteorlxy]

Would introduce lots of breaking changes for sure.

[devPaulRS]

@meteorlxy | @Mister-Hope

I see you guys have started to combine the client config file, but this doesn't seem to be ready yet for theme config. Any chance of adding this anytime soon?

I would like to have the navbar and menu being set in the client.ts/client.js and would very much appreciate it as it would stop the restarting the server everytime i dynamically add a menu item.

Also if possible when this is added as a request that we can have a nice detailed example with the navbar in the vuepress documentation, as it would make a lot of people happy.