Hmm. I'm not sure what is wrong. I don't have a Google store developer account, otherwise I would have published it there.
Try this as a workaround:
- clone the repo
- go to chrome://extensions/
- enable "Developer mode"
- Click on "Load unpacked extension..." and select the cloned directory
The advantage of this method is that you will be able to upgrade the extension in the future with a git-pull!