Embed RichFilemanager I want to embed RichFilemaneger (https://github.com/servocoder/RichFilemanager) in a Drupal-8 site. RichFilemanager has its own index.html and a php-conncetor for implementation in other sites. 

But it's not clear to me which approach to follow.

Should i keep RichFilemanager in it's own directory in the Drupal-root and connect to it via the php-connector? In that case it seems to me that Drupal can't take care of the security...
or should i copy the content of the index.html to a twig template? But that would make it hard to keep up with updates of RichFilemanager.

Can anyone point me in the right direction?
Are there similar tools implemented which i could use as an example?
You should include it with composer to your Drupal project. That is step one. You don't need to consider package management - composer will do this for you.

How you wire it up from there is basically up to you and your use case. I assume first you start with a basic controller and go from there in a custom module.