- fixed some `<link>`, `<meta>` and `<script>` tags not being included in `<head>` when a file was excluded from post-processing
- added `theme` command-line option
- added `html_header` config option option
- added automatic generation of github links in changelog when config option `github` is set
- added new light theme
- added dynamic switch for dark/light theme
- removed text from github icon on navbar (5) (wroyca)
- removed excessive spacing between article sections (5) (wroyca)
- many minor style fixes and tweaks