Multiple images selection from photolibrary or savedphotoalbum

# Feature Request
Multiple images selection from photo library or saved photo album (Configurable Parameter).

## Motivation Behind Feature
As of now, we can configure the camera plugin to select an image from the gallery (photo library/saved photo album). It would be great to add a config option like `maxImageCount` which can default to 1 by default.

There is no ionic plugin as of now which gives us the option of selecting multiple images in one go apart from [ImagePicker](https://github.com/Telerik-Verified-Plugins/ImagePicker). The drawback of this plugin is that it shows a view where all images are shown together i.e. no album based grouping etc. etc

Camera plugin by default opens the native android's browser which lets us choose an image from albums, lets us open some another application for choosing the image (something like a gallery app). Adding multiple selections will be really really helpful.

## Feature Description
I am expecting something like this

```js
options: CameraOptions = {
quality: 100,
destinationType: this.camera.DestinationType.FILE_URI,
mediaType: this.camera.MediaType.PICTURE,
sourceType: this.camera.PictureSourceType.PHOTOLIBRARY,
saveToPhotoAlbum: false,
maxImagesCount: 15 // defaults to 1
}
```
**NOTE: -** The `maxImagesCount` option will only work if the `sourceType` is set to `PHOTOLIBRARY` or `SAVEDPHOTOALBUM` & `mediaType` is set to `PICTURE`.

_Also for the initial stage cropping, changing orientation etc for multiple file selection can be kept off._

## Alternatives or Workarounds
As of now, there are no workarounds or alternatives!

I think we should take a count of users who would love to have this feature in the plugin. To all the developers working on this plugin you guys are doing a great job & Thanks a lot in advance :+1: