There are two main ways to support ClaimChunk; the first is donating to the author, CJ Burkey. The second option is creating pull requests & issues.
I appreciate all the forms of support players and server maintainers have given me over the past couple of years with this plugin; I would like to keep this small, respectful community of everyone a welcoming place for everyone and I appreciate everyone else willing to help :)
Creating an issue for an unexpected behavior you notice while using the plugin or missing expected behavior is probably the simplest way to make a good impact on the plugin. Make sure to include as much information as possible, and I'll do my best to locate and fix the bug responsible. There are also feature request issues which, much like they sound, describe some sort of feature that ought to exist but doesn't at the present. There are, of course, plenty of different types of issues and suggestions a plugin could receive and you're not limited to those two specifically.
Pull requests are how Github handles other people adding code into the repo. I'm going to be entirely honest here: I've never made a pull request, which is definitely weird now that I think about it. That being said, the process to develop one is documented here on Github's documentation. You're more than welcome (and even encouraged) to submit your own pull requests to address certain features/bugs, especially if I'm difficult to reach for a couple days, or even if you just want to help out.