New theme adapted from bugzilla.mozilla.org

This is an attempt at adapting the bugzilla theme used in https://bugzilla.mozilla.org to the bugzilla instance used by KDE.

This theme has both light and dark version which will be applied automatically depending on the browser's dark mode preference settings. Some screenshots of the new theme is given in the table below (with dummy data copied from bugs.kde.org).

Current Theme	New Theme