Update server documentation with new mmproj configuration options

[kth8]

The LLaMA.cpp HTTP Server README currently lacks documentation for the new mmproj configuration options, which were updated in #13416 that can be set via command line arguments or environment variables.

[ngxson]

It's already there, please read the doc carefully:

[kth8]

@ngxson I saw https://github.com/ggml-org/llama.cpp/blob/master/docs/multimodal.md but that doesn't document all the mmproj command line options along with their corresponding environment variables like the server README does. I think it would be beneficial to have all the command line arguments and environment variables documented in a central place for easy discoverability.

[ngxson]

It will be addressed in #13432

It's not a really related issue, but because the table is auto-generated, we do a periodically update of the list of args