To contribute, you should first fork and clone the project locally. You can, of course also edit the project online, that's up to you.
Just add your package manager of choice at the back of the Language section where it belongs. If there isn't one, create a new one. Just be sure to add an anchor link to it. You can also include a short description of the package manager you added.
Try to keep the index sorted alphabetically.
IMPORTANT: Please mark it if your package manager is official to the language or framework!
After you made your edits, just submit your PR here and wait for it to be approved!