Developing for HAX itself or leveraging it's tools? There's a lot going on in our ecosystem so if we miss something let us know!
The HAX monorepo has all 500+ blocks in the HAX ecosystem, as well as the editor, site and CMS (front-end) aspects of the system. If contributing to ANYTHING front-end focused, it will be through this repository. General contribution workflow:
yarn install
yarn run hax
from the project rootcd elements/element-name
and then run yarn run start
The HAX CLI is the best way to accomplish this. It leverages Lit + OpenWC recommendations for building new web components that can easily be published on npm. It also has boilerplate that makes it easier to build blocks that visually look like the HAX ecosystem (via DDD) and also ways of creating stand alone HAXsite's and workflows for building custom themes and elements for the ecosystem.
Each project whether HAX11ty, haxcms-nodejs, haxcms-php, HAXiam, unbundled-webcomponents, no matter what it is, it will have it's own repository for contribution.