Add dependencies to composer.json

[luksak]

Currently there are no dependencies in composer.json:

{
  "name": "drupal/media",
  "description": "Media module for Drupal",
  "type": "drupal-module",
  "homepage": "https://github.com/drupal-media/media/",
  "support": {
    "irc": "irc://irc.freenode.org/drupal-contribute"
  },
  "license": "GPL-2.0+",
  "minimum-stability": "dev",
  "require": { }
}

But media.info.yml declare a bunch of dependencies:

name: Media
description: 'Media module for Drupal 8'
type: module
package: Media
core: 8.x
dependencies:
  - media_entity:media_entity
  - media_entity_image:media_entity_image
  - video_embed_field:video_embed_field
  - video_embed_field:video_embed_media
  - media_entity_slideshow:media_entity_slideshow
  - media_entity_instagram:media_entity_instagram
  - media_entity_twitter:media_entity_twitter
  - media_entity_document:media_entity_document
  - slick_media:slick_media
  - entity_browser:entity_browser
  - entity_browser:entity_browser_entity_form
  - entity_embed:entity_embed
  - dropzonejs:dropzonejs_eb_widget
  - image_widget_crop:image_widget_crop
  - link:link
  - editor:editor

I guess we should fix that.