Add support for PDF content type

### Feature Description

Add support for PDF content type "application/pdf"

```go
ctx.Data(http.StatusCreated, "application/pdf", nil)
```

<img width="577" height="495" alt="Image" src="https://github.com/user-attachments/assets/33ee8471-433e-496b-8af5-435dc8a4cccb" />