The add-on lives in Google's Script Editor but, in keeping with best practices, this repo is the source of truth, and the script editor will be overwritten with local changes.

To start developing, you will need to create a blank Script Editor project.

In order for this to work, you will need to follow the first 2 steps of the Quickstart for node-google-apps-script. I recommend "Independent Developer Console Project" for step 1.

You should only need to do this once. Once you have gapps auth working you will need to rename gapps.config.json-sample to gapps.config.json and put in your script's id. Finally, run

npm run deploy

This will use node-google-apps-script to upload the dist directory to the add-on's script editor.

In the script editor choose "Publish" → "Test as add-on…" and then select a document to test with.

That will open a new window with your document. You will then see your project in the Add-ons menu.