There's no way to require it. The best you can do is tell the user to do it.
Also, it use require.main.require instead
It's been a while since I made a plugin for you lovely people. So here you go.
Just paste the imgur link into a post with this plugin enabled and it'll embed into the page. This plugin doesn't affect the nodebb-plugin-imgur plugin that @baris made and can be run side by side. If you wish for your uploaded images to be embedded in the same embed window rather than full screen, just remove the file extension on the end of your uploaded image.
Galleries appear as a slideshow and support gifv and whatever other format imgur uses.
As always, bugs may appear, sometimes imgur provides a link that includes a # followed by another random string of characters, when I have a little more time to refine the plugin I'll strip that out.
npm install nodebb-plugin-embed-imgur