Here's an example using SVG path and clip-path: https://codepen.io/wildpeaks/pen/eYXMxoP

Comes standard on Squarespace (which I've liked except for the expense) in the WYSIWYG post editor. I would not know how to make them from scratch.

It's a SVG path (look for element ".TextShape-node" in devtools), most likely animated using a rect "clip-path".