docs: update README.md with REST Service section and GitHub stars badge (camel-ai#401)

* Update README.md to improve structure and clarity. Removed redundant section on Graph Service and added a new section for REST Service. Included a tip about the MCP server for enhanced user guidance.

* Add GitHub stars badge to README.md for enhanced visibility

Author: danielchalef

README.md

@@ -14,6 +14,7 @@ Graphiti
 [![Unit Tests](https://github.com/getzep/Graphiti/actions/workflows/unit_tests.yml/badge.svg)](https://github.com/getzep/Graphiti/actions/workflows/unit_tests.yml)
 [![MyPy Check](https://github.com/getzep/Graphiti/actions/workflows/typecheck.yml/badge.svg)](https://github.com/getzep/Graphiti/actions/workflows/typecheck.yml)
 
+![GitHub Repo stars](https://img.shields.io/github/stars/getzep/graphiti)
 [![Discord](https://dcbadge.vercel.app/api/server/W8Kw6bsgXQ?style=flat)](https://discord.com/invite/W8Kw6bsgXQ)
 [![arXiv](https://img.shields.io/badge/arXiv-2501.13956-b31b1b.svg?style=flat)](https://arxiv.org/abs/2501.13956)
 [![Release](https://img.shields.io/github/v/release/getzep/graphiti?style=flat&label=Release&color=limegreen)](https://github.com/getzep/graphiti/releases)