Automatic Unit Converter

WebExtension (originally created for Mozilla Firefox, not tested on other browsers) that replaces (American) units to their SI/Europian counterparts.

Currently only the english convention is converted (comma as separator between thousands and points to represent floating point numbers).

Thus far implemented:

1. lbs/pounds to kg

2. fahrenheit to celsius

Based on example that can be found here: https://github.com/mdn/webextensions-examples/tree/master/emoji-substitution