First off, thank you for considering contributing to MediaManager.
Following this guide helps me merge your PRs faster, prevents unnecessary back-and-forth and wasted effort.
Open an issue which describes the feature you would like to see, why you need it, and how it should work. There we can discuss its scope and implementation.
Generally, if you have any questions or need help on the implementation side of MediaManager, just ask in the issue, or in a draft PR.
Also, see the contribution guide in the docs for information on how to setup the dev environment: https://maxdorninger.github.io/MediaManager/
Make the change, and open a PR with a short description of what you changed and why.
Explain why you are making the change. Be sure to give a rough overview on how your implementation works, and maybe any design decisions you made. Also include any relevant limitations or trade-offs you made.
It's best to also open an issue first to discuss larger changes before you start working on them.