FGIA is a Wordpress plugin to add a group of images into our Wordpress post.
Download the zip of this repository or clone it into your your-wordpress-site/wp-content/plugins folder.
In your admin panel, go to Plugins and activate the plugin.
Now, when you go to a post, you can see a new button in your editor bar.
Now, just click on "Insert images" button.
Don't forget to add some style in your editor-style.css