Add Shutterstock (#2258)

README.md

@@ -1029,6 +1029,7 @@ API | Description | Auth | HTTPS | CORS |
 | [Pixabay](https://pixabay.com/sk/service/about/api/) | Photography | `apiKey` | Yes | Unknown |
 | [PlaceKitten](https://placekitten.com/) | Resizable kitten placeholder images | No | Yes | Unknown |
 | [ReSmush.it](https://resmush.it/api) | Photo optimization | No | No | Unknown |
+| [shutterstock](https://api-reference.shutterstock.com/) | Stock Photos and Videos | `OAuth` | Yes | Unknown |
 | [Unsplash](https://unsplash.com/developers) | Photography | `OAuth` | Yes | Unknown |
 | [Wallhaven](https://wallhaven.cc/help/api) | Wallpapers | `apiKey` | Yes | Unknown |
 | [Webdam](https://www.damsuccess.com/hc/en-us/articles/202134055-REST-API) | Images | `OAuth` | Yes | Unknown |