Sample doc for custom model server using multi-model serving

[Aaronchoo]

/kind feature

Describe the solution you'd like
[A clear and concise description of what you want to happen.]
Add a sample of MMS using a custom model server similar to sklearn and triton that will reside in the same directory.

Anything else you would like to add:
[Miscellaneous information that will assist in solving the issue.]
This should include how to specify supported framework and how to set protocol and multi-model server ref.

[molejnik-mergebit]

+1 on this, I would really appreciate some docs as this is not clear in kserve 0.8.0 how to get multi model serving to work

[Samjoel3101]

Hi , I am new here would love to work on this documentation I have just started to explore the multi model serving part of kserve. Would love to explore this further and work on the documentation of this if I get the chance. @yuzisun @Aaronchoo