Here is how to do it:

1. Create a new repo and give it a name exactly as your username is. For example, my username is gk3000, I would create a repo and name it gk3000.
2. In this repo create a file readme.md
3. Using markdown add any content into this file.
4. That's it!

Here is a link to the markdown reference: https://www.markdownguide.org/basic-syntax/

Now when someone will go to you GitHub profile they will see the content of this file properly rendered with all sorts of content like images, links, emojis, etc...

👻