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CloseDeveloper reply by ChoGGi
Rated 5 out of 5 stars
Thanks for answering,
Do you have in your plans to make it to work with FF 57?
If the WebExtensions API doesn't support it, nothing I can do.
As long as FF keeps support for UserChrome.css, you can still manually add the CSS (just stick the mosaic in the same folder as userchrome.css).
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