Add NexusRaven 13B V2 model

[JamesClarke7283]

Is your feature request related to a problem? Please describe. Add a new model to the gallery: NexusRaven V2: "NexusRaven-V2 is capable of generating single function calls, nested calls, and parallel calls in many challenging cases." - Nexus team.

Describe the solution you'd like Add the model template to the gallery with grammers that utilise its full function calling ability.

Describe alternatives you've considered N/A

Additional context URL: https://huggingface.co/Nexusflow/NexusRaven-V2-13B

Function calling leaderboard: https://huggingface.co/spaces/Nexusflow/Nexus_Function_Calling_Leaderboard