To contribute by adding a new pattern, you can use the hugo new pattern/.md and it will generate a file in the right place. Else you can just copy an existing .md file from the pattern directory in order to create a new one. If you require additional tags, you have to add them to the pattern_types taxonomy as _index files in "/content/pattern_types/<pattern_type_name>/" and it will be usable as taxonomy element.
We are also collecting code samples as gists, and you can use the "singleton_java" as a reference. (hint, you can add the gist in the "gists" list within the front matter of the codesample)