A repository made for the beginners in GitHub to get used to it
Just write .md file related to the topic you know about to explain it, can also add the maths behind it... literally anything !! and venture to the open source world
This would help you to create pull requests, issues , get it merged and get used to the real open source environment.
Also you could add any new topic you want to add in the issues... I will suggest and reply to you ASAP whether to do it or not.
You could also expand the horizon to any other development/coding topics !!!!
Enjoy Github :)