How to pass configuration when running vls from command line?

Hello,

I would like to use `vim-language-server` with https://github.com/autozimu/LanguageClient-neovim
but I (as not Node developer) have no idea how to pass the configuration presented for `--stdio`.

With
```vim
let g:LanguageClient_serverCommands['vim'] = [exepath('vim-language-server'), '--stdio']
```
seems to work, but I would like to configure `fromRuntimepath` and not only.

Seriously: I even not know how to list possible options... Running `vim-language-server` without parameters throws the error with suggestion to use only the basic
```
'--node-ipc', '--stdio' or '--socket={number}'
```
but not how to display help message and how to inject any configuration.

Please complete documentation.