DecoratedRequest typing support to Query, Headers and Params

Nobody has claimed this yet.

## The feauture or bug you are proposing

Extend `DecoratedRequest` TypeScript support to Querystring, Headers and Params too.

## The description of the bug or the rationale of your proposal

Right now the `[DecoratedRequest interface](https://github.com/mia-platform/custom-plugin-lib/blob/9f20da345f208c391527c9c74e4bb7bcbc2955c2/index.d.ts#L60)` allows to specify the Generic only for the inner FastifyRequest body, meaning that if I can't specify the shape on any other request parameter (being Querystring, Headers or Params).

## A snippet of code for replicating the issue or showing the proposal usage if applicable

```

interface HelloQueryParameters {
who?: string
}

interface HelloRequest {
Querystring?: HelloQueryParameters
}

service.addRawCustomPlugin('GET', '/hello', async function (request:DecoratedRequest, reply:FastifyReply) {
return { message: `Hello ${request.getUserId() || (request.query as HelloQueryParameters).who}` }
}, schema)
```

In the snippet above, `request.query` is threated as `unknown`

## The expected result for your bug

```

service.addRawCustomPlugin('GET', '/hello', async function (request:DecoratedRequest, reply:FastifyReply) {
return { message: `Hello ${request.getUserId() || request.query.who}` }
}, schema)
```

### Your environment

node: v12.17.0
custom-plugin-lib: `@mia-platform/custom-plugin-lib@4.1.1`
os: MacOS

Start with the DecoratedRequest interface in index.d.ts, especially the generic currently used for the FastifyRequest body. Check how query, headers, and params are typed, then verify that the HelloRequest example can access request.query.who without a cast while preserving existing body typing.

Written by the indexing model from the issue text.