Go to our official repository and make an Issue detailing what the feature should be. Explain why it would be a good addition and explain how it fits in with the rest of the language. Make sure to consult our Philosophy as well.
Create a new branch of our official repository, add a document to the Docs/ folder, and make a pull request. The JAJL team will look into it.
If you see a bug and can fix it, make a branch, fix the bug, and make a pull request.
Create an Issue.
Create an Issue.