make adress bar icon lighter when Firefox uses dark theme

[Erstal70]

The adress bar icon is too similar to the background when Firefox uses dark theme.

Make the icon use similar lightness of gray color as the native Firefox adress bar icons.

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[poison borz]

This is resolved with the new version, it has now the same grey color as the other icons

[Pierre-Adrien Buisson]

Thanks for the update! I close this issue.