htmx allows you to access AJAX, WebSockets and Server Sent Events directly in HTML, using attributes, so you can build modern user interfaces with the simplicity and power of hypertext
You may also be interested in ...
NES.css
NES.css is NES-style (8bit-like) CSS Framework.
Mizujs
mizu.js is a lightweight HTML templating library designed to simplify web development.
Sal.js, lightweight scroll animation library
Sal (Scroll Animation Library) is written with aim to provide performant and lightweight solution for animating elements on scroll. It's based on the Intersection Observer, which gives amazing performance in terms of checking the element's presence in viewport.