Add performance benchmarks page

[AmitoVrito]

Description

Add page showing SynapseKit's performance benchmarks.

What to do

• Create docs/benchmarks.md
• Benchmark: import time, RAG query latency, streaming TTFT, memory usage
• Compare with LangChain (same setup, same model)
• Show graphs/charts
• Re-run for each release

[AmitoVrito]

Thanks for your interest! I will assign it to you. Before you start, could you give the repo a ⭐ on the main repo (https://github.com/SynapseKit/SynapseKit)? It really helps with visibility for a new project. Looking forward to your PR!