Convert GitHub or Gist contents to PDF by removing unnecessary elements.
First, you need to change into the directory and install all NodeJS dependencies with npm or yarn:
npm install
Start the continuous build process to transpile the code into something that can run in Firefox or Chrome:
npm run build
This creates a WebExtension in the extension subdirectory. Any time you edit a file, it will be rebuilt automatically.
In another shell window, run the extension in Firefox using a wrapper around web-ext:
npm start
Any time you edit a file, web-ext will reload the extension in Firefox.