Hi,
I would like to know how I can contribute my own libraries (I mean, the ones I make) to the Arduino project.
Hoping for a reply,
Sam 
You could add them to github and then share the links
Once you have published your libraries on GitHub, you can add them to the Arduino Library Manager index. That provides the easiest method for users of the Arduino IDE and arduino-cli to install and update your library. They will get a notification whenever a new version of any library installed via Library Manager is available and can update to that new version with a few clicks. All libraries in the Arduino Library Manager index are pre-installed in the Arduino Web Editor so that means web editor users don't even need to think about installing your libraries.
There are instructions for preparing your library and submitting it for inclusion here:
Please let me know if you have any questions.
I wrote this some time ago, may be helpful