![](https://lemmy.ml/pictrs/image/a64z2tlDDD.png)
A lot of people are recommending version control. While it's good practice, that isn't a requirement of sharing your code. If you want to make it really simple at first, add a License (as others have mentioned) and just post the code anywhere. Upload a tar archive to a website, use sourceforge or even lemmy.
Learning git would still be useful for you and potential contributors but it is not a requirement. Open source just means you share the source and explicitely provide a license for others to use and modify it
What's wrong with the pretty gray background?