fathom-webextension
Simple popup that extracts and displays the product title, image, and price when run on product detail pages (one main product). Uses fathom-products rulesets (https://github.com/swathiiyer2/fathom-products). Fathom-products uses a Mozilla Javascript framework called Fathom (https://github.com/mozilla/fathom).
Usage
Go to about:debugging in Firefox. In the add-ons tab, click 'Load Temporary Extension', and choose any file in this repo. Visit any product detail page and click the popup to see it's details!