Type of templates property in PointOfViewOptions show allow arrays

Prerequisites

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

Fastify version

4.9.2

Plugin version

7.1.2

Node.js version

18.12.0

Operating system

Linux

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

22.04

Description

As per the example for Nunjucks, an array of strings should be allowed for the templates option (at least for Nunjucks):

https://github.com/fastify/point-of-view#nunjucks

However, it is currently typed as an optional string, so passing an array of strings is currently a type error:

https://github.com/fastify/point-of-view/blob/2124f9e3ef0d771fbefd65aeecb94a8943b8d7df/types/index.d.ts#L33

(Can currently be worked around using as unknown as string on the array.)

Steps to Reproduce

Compile:

import fastify from 'fastify'
import nunjucks from 'nunjucks'

const server = fastify()

server.register(fastifyView, {
  engine: {
    nunjucks,
  },
  templates: [
    'test',
    'test2',
  ],
})

The following type error is returned:

 error TS2769: No overload matches this call.
  Overload 1 of 3, '(plugin: FastifyPluginCallback<PointOfViewOptions, RawServerDefault, FastifyTypeProviderDefault>, opts?: FastifyRegisterOptions<...> | undefined): FastifyInstance<...> & PromiseLike<...>', gave the following error.
    Type 'string[]' is not assignable to type 'string'.
  Overload 2 of 3, '(plugin: FastifyPluginAsync<PointOfViewOptions, RawServerDefault, FastifyTypeProviderDefault>, opts?: FastifyRegisterOptions<...> | undefined): FastifyInstance<...> & PromiseLike<...>', gave the following error.
    Argument of type 'FastifyPluginCallback<PointOfViewOptions, RawServerDefault, FastifyTypeProviderDefault>' is not assignable to parameter of type 'FastifyPluginAsync<PointOfViewOptions, RawServerDefault, FastifyTypeProviderDefault>'.
  Overload 3 of 3, '(plugin: FastifyPluginCallback<PointOfViewOptions, RawServerDefault, FastifyTypeProviderDefault> | FastifyPluginAsync<...> | Promise<...> | Promise<...>, opts?: FastifyRegisterOptions<...> | undefined): FastifyInstance<...> & PromiseLike<...>', gave the following error.
    Type 'string[]' is not assignable to type 'string'.

Expected Behavior

No type error.

fastify / point-of-view

Type of templates property in PointOfViewOptions show allow arrays #352