Support for bigint

[Forceres]

Prerequisites

• I have written a descriptive issue title
• I have searched existing issues to ensure the bug has not already been reported

Fastify version

5.6.1

Plugin version

8.2.0

Node.js version

22.18.0

Operating system

Linux

Operating system version (i.e. 20.04, 11.3, 10)

ArchLinux

Description

If you pass the object with bigint values, it gives you an error.

Link to code that reproduces the bug

/

Expected Behavior

Successfully serialize bigint.
You can use replacer for JSON.stringify at least.