Heroicons by Tailwind
Speaking of Tailwind, they have a cool icon repository now (although it looks like there was a "classic" version so maybe they've done them forever). Easily just cut and paste the SVG code from your browser.
This is my favourite way to add icons, because its so much simpler than any other method, but also you can style and animate them. Its odd there are no social icons included. The Twitter and Github icons on the site seem like they are the same format and size... 👀