Setup

git clone https://github.com/typestyle/typestyle.git
npm i

Dev

npm start

Think if your change is major (breaking api) / minor (potentially breaking but you tried your best not to) / patch (safe).
See current version in package.json and update CHANGELOG.md adding the planned release version notes.
Commit all your changes (including changelog)
Run npm version major|minor|patch. It will automatically push to github, run npm publish on your behalf.