Add redis to contributor guide (#7369)

## Context

We are adding redis to default twenty configuration. 

## What

1. This PR sets up the local setup for contributors accordingly

2. I'm also updating the code blocks guide:

Before:
<img width="921" alt="image"
src="https://github.com/user-attachments/assets/2203cc99-b5a5-4d05-a8b1-98a348aee9df">


After:
<img width="921" alt="image"
src="https://github.com/user-attachments/assets/5b3e6f34-723d-4309-888b-c02ce794891d">

packages/twenty-website/package.json

@@ -14,6 +14,8 @@
     "database:generate:pg": "npx drizzle-kit generate:pg --config=src/database/drizzle-posgres.config.ts"
   },
   "dependencies": {
+    "@docsearch/react": "^3.6.2",
+    "gray-matter": "^4.0.3",
     "next-runtime-env": "^3.2.2",
     "postgres": "^3.4.3"
   }