Better code snippets for llama2 models

[beurkinger]

Is your feature request related to a problem? Please describe.
The code snippet we propose for llama2 models would technically "run" but the results will not be great.

Describe the solution you'd like
Add custom snippets for llama2 models. Maybe add a perRepo param etc.

[osanseviero]

cc @xenova . Now that we have jinja.js, we could use this to provide better snippets for the endpoints