fix: correct slugifyTitle hook example in documentation

[AntonAmbarov]

What?

Fixed incorrect return statement in the slugifyTitle field hook example in the official documentation.

The example was generating a properly formatted slug but then incorrectly returning the original value instead of the slugified result.

Why?

This was a bug in the documentation that could mislead developers implementing automatic slug generation. The hook appeared to work, but in reality did nothing useful.

How?

• Changed return value to return slug in the example

Before/After

Before:

const slug = value.toLowerCase()... 
return value // ← bug

**Aftere:**
```ts
const slug = value.toLowerCase()... 
return slug