The centralize image feature looks very interesting, feel free to open a pull request for that feature and we can take a look at it!
You can read our contributing guideline file for more information. It contains links to help you out if you are new to git! :) https://github.com/Orama-Interactive/Pixelorama/blob/master/CONTRIBUTING.md#cont...
To create a fork, you have to go to the original repository (https://github.com/Orama-Interactive/Pixelorama) and on the top right, click "Fork". This will created a forked repository in your account. As for the rest, this guide does a fantastic job at explaining the process! https://akrabat.com/the-beginners-guide-to-contributing-to-a-github-project/