Hi there,
if its in the Editor then that is a feature of the GenerateBlocks plugin.
It will accept any valid SVG HTML code. A good place to start is with FontAwesome icons – this article explains how to extract them and add them:
https://docs.generateblocks.com/article/adding-custom-svg-icons/
You can use the same process for any icon library.
Mike one of our Site designers provides a couple of other icon sites here:
https://generatepress.com/forums/topic/svg-icons-origin/#post-1677527
And he also found this one recently – which provides the HTML in the site 🙂
https://icons.getbootstrap.com