consider compatibility with Firefox

This is neat, particularly since it's a webextension, and so in theory should be compatible with most browsers. Unfortunately it doesn't "just work" in Firefox yet - have you considered investigating the compatibility issues and supporting Firefox? If it there are platform issues, I could potentially help get them resolved.

Here's some documentation if it's helpful: https://developer.mozilla.org/en-US/Add-ons/WebExtensions

Start by reproducing the extension's behavior in Firefox and compare the affected APIs with the linked Mozilla WebExtensions documentation. Identify the compatibility issues before deciding the scope; done means the extension works in Firefox, with the relevant behavior verified there.

Written by the indexing model from the issue text.