Typescript: how to handle arrays or toMany relations

Hey,

while I was working on an Angular generator I noticed that the current implementation of the typescript interface generator does not take into account toMany relations (or simple arrays as well).

I had a look at the `fields` property inside `resource`, however I can't seem to find any difference between single fields and array fields. I hoped that the `maxCardinality` property would help me, but it seems properly populated only for reference types.

Here is an example of what I mean:

Resource definition
```PHP
/**
* @ORM\Column(type="text", nullable=true)
* @Groups({"producerRead","userRead"})
*/
private $name;

/**
* @ApiSubresource()
* @ORM\OneToMany(targetEntity="App\Entity\Product", mappedBy="producer", orphanRemoval=true)
* @Groups({"producerRead","userRead"})
*/
private $products;

/**
* @ORM\OneToOne(targetEntity="App\Entity\Picture", cascade={"persist", "remove"})
* @Groups({"producerRead","producerWrite"})
*/
private $mainPicture;

/**
* @var array
* @Groups({"producerRead","producerWrite"})
*/
public $test;
```
Dump of resource.fields (part of id) inside the `generate` function
```
Field {
name: 'products',
id: 'http://localhost:8080/api/docs.jsonld#Producer/products',
range: 'http://localhost:8080/api/docs.jsonld#Product',
reference: [Resource],
required: false,
description: '',
maxCardinality: null,
deprecated: false },
Field {
name: 'name',
id: 'http://localhost:8080/api/docs.jsonld#Producer/name',
range: 'http://www.w3.org/2001/XMLSchema#string',
reference: null,
required: false,
description: '',
maxCardinality: null,
deprecated: false },
Field {
name: 'mainPicture',
id: 'http://localhost:8080/api/docs.jsonld#Producer/mainPicture',
range: 'http://localhost:8080/api/docs.jsonld#Picture',
reference: [Resource],
required: false,
description: '',
maxCardinality: 1,
deprecated: false },
Field {
name: 'test',
id: 'http://localhost:8080/api/docs.jsonld#Producer/test',
range: null,
reference: null,
required: false,
description: '',
maxCardinality: null,
deprecated: false },
```

In the swagger docs the property `test` is correctly picked up as a string array, however I can't seem to replicate the same thing for the typescript interfaces.

If we look at `maxCardinality`, it seems it is correct (if we assume null means 'collection') for reference fields (mainPicture is a OnetoOne and products is a ToMany), however this is not the case for `name` (string) and `test` (string array).

I'm asking here because there might be another field that helps me find out if I'm dealing with a collection or not and I'm missing it, but this issue might be related to doc-parser as well.

I'll gladly create a PR for the typescript generator if we find out how to fix this. Thanks!