Beta 4 of Margen, the final version. Four additions.

Code syntax highlighting via highlight.js. Code blocks in the preview now
get colored based on language. Works in dark mode too.

Export and import. An export button downloads the current note as a
standalone HTML file with markdown, LaTeX and code already rendered, and
opens the print dialog so you can save it as PDF. An import button lets
you load an existing .md file as a new note.

PWA installable. A service worker caches the core files so the app works
offline on desktop and Android. The manifest is generated dynamically.
CDN assets like KaTeX and highlight.js are not cached to avoid bloat, so
formulas and code highlighting need internet the first time, but the app
itself, your notes and the markdown parser all work offline.

Calling Margen done. Four betas: basic editor, parser fix and cheat
sheet, LaTeX and dark mode, now code highlighting, import, export and
PWA.