How can I get social butons like this?

I want to have social buttons like this on left side of my whole browser. Just like here https://filament.io/applications/flare

When I see something on the web that I like - or want to learn more about - I use View Source to see how it is done.
Unlike traditional software development, with content for the web the ‘source code’ is visible and available to be studied by anyone.

From the very beginning of the [public] Internet, I have used that technique to learn HTML, Javascript, CSS, et cetera.