Specifically, the old highlighter didn't support the "diff" format which was important for changelogs.
Changed the style from dark to light, since it's way too contrasty on a light background - makes it hard to scan both text and code.
And reduced the padding between code and content (mostly using the highlight style defaults)
Added a slight background shadow on code to visually offset the relatively light background color
Changed existing background color for <pre> to a slightly lighter shade, better contrast
Didn't create a custom *.ss style yet, too much work, and XML is good enough for now
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