Firefox extension

[matiasvad]

This pull-request will cause errors in Chrome, since it uses a parameter in the manifest which Chrome doesn’t recognize.

Your checklist for this pull request 🚨Please review the guidelines for contributing to this repository.

[] Make sure you are requesting to pull a topic/feature/bugfix branch (right side). Do not pull request to Master please.(when in doubt request Develop branch) [] Test to make sure your feature/bugfix doesn't break other features ;) [] Write a meaningful description of what your changes are. [] Wait patiently and celebrate, you've submitted changes to the extension!

Description Please describe your pull request.

<3 Thank you!