Stable release 2.88.3

What's Changed

• Fix #525: typo in URL to upstream DB stylesheet
• HTML: Make more space for cover icons by @tomschr in #527
• Fix #526: add book titlepage for TRD stylesheets by @tomschr in #528
• Support return for keycaps by @tomschr in #529

Full Changelog: 2.88.2...2.88.3

Thanks to:

• @navin772