How to include javascript file in kirbytag plugin

I’m writing an extended version of the video kirbytag and need to include some javascript code. As recommended in the docs my plugin folder structure is:

site/plugins/bettervideo/index.php
site/plugins/bettervideo/assets/bettervideo.js
site/plugins/bettervideo/tags/bettervideo.php

I read on the plugin-basic docs page that

Each asset in the assets folder of your plugin will be available at /media/plugins/superwoman/superplugin/ .

and this about timestamps and urls

Asset folder
/site/plugins/superplugin/assets/fields/myfield.js

Public URL
/media/plugins/superwoman/superplugin/fields/myfield.1520265293.js

but don’t know where and how to import the js file.

This is my first plugin so I probably am missing something really obvious but can’t find an answer anywhere (neither here nor on other pages of the docs). Thanks for any help.