Inform these folks when it's made. https://www.reddit.com/r/firefox/comments/hlyy8h/addonrequest_round_all_online_retail_prices_up_to/ This tought me about parsing all the text: https://github.com/mdn/webextensions-examples/blob/master/emoji-substitution/substitute.js This might teach me about storing data and creating settings: https://github.com/mdn/webextensions-examples/tree/master/favourite-colour This might also teach about settings: https://github.com/mdn/webextensions-examples/tree/master/beastify Load in firefox 1. Go to: about:debugging 2. Click "This Firefox" 3. Load the `manifest.json` file.