Most ClickStarts you can see on the CloudBees UI are developed in the CloudBees-community GitHub account. This account has been set so you can contribute your fixes/improvements, just fork a repo, make a change, give it a try, and create a pull request.
A ClickStart, technically speaking, is a simple JSON file. Let's have a look at one of the CloudBees' ClickStarts, for example, Play2. The following screenshot demonstrates ClickStart hosted on GitHub:
README.md file is common in GitHub repositories, but it makes more sense here as it's the simplest way to let another user test your ClickStart, as the Deploy Instantly on ...