This extension is pretty unlike most of the examples the chrome docs provide because it extends the devtools which most extensions don't do. There are a lot of hidden gotchas you have to look out for when extending devtools and the api they provide just isn't as well thought out. However I actually made the first version of this extension when I was just starting out learning html/css/js and I think it was good project for that. I wouldn't worry about making something presentable for the webstore at first. Just build whatever you need with really bare bones UI and iterate if you forsee it being useful for other people. Maybe even start with a greasemonkey script.
