First order of business, Hello everyone! I'm new here and a pretty active Wordpress User/Builder
There are a several wordpress plugins using some of the GSAP libraries. 2 that haven't been maintained since last year (LivIcons Evolution and AnimateWP from codecanyon) and there are right now 2 recent plugins fully compatible with wp 5.3 in the WP repository and plugin pages.
Advanced WordPress Backgrounds, found here: https://wordpress.org/plugins/advanced-backgrounds/
and
Scrollsequence – Fullpage Scroll Image Animation Plugin, found here: https://wordpress.org/plugins/scrollsequence/
Revolution Slider and Kreatura LayerSlider have both had code fixes for GSAP (I'm assuming gsap3 by the dates) about 2 build versions back according to both of their changelogs.
There is also a write up and GIT about creating a custom plugin to add sitewide support for GSAP,
Article: https://medium.com/@pixeldroid/gsap-in-wordpress-9e5771a059a
Accompanying plugin template: https://github.com/eightbit/eightbit-resources/blob/master/GSAP-in-WordPress.zip
Last of all is another article saying this is the right way to add gsap3 support (Of course, without the codepen only plugins,, obviously..):
https://www.owlasylum.net/downloadthisweb/greensockgsap-3-proper-wordpress-5-integration-and-enqueuing/
The simplest and best option would be the very last link. Less of a chance of having to redo anything due to a template or plugin update if you were to add code to either. I haven't tested any of it yet since I've only today come across GSAP with codepen examples and had been looking to do more with Revolution Slider, Smart Slider 3 or Kreatura LayerSlider (animations, text effects etc..). I had already replicated all my slides into the others incase I had to change to one of them so if I had to switch, it wouldn't be a big deal. Cheers all!
**Edit**
Almost forgot about the new c9 blocks plugin for the WP Gutenberg editor, Article: https://www.covertnine.com/c9-blocks-plugin/
GIT: https://github.com/covertnine/c9-blocks