I decided to investigate the bundle size for misode.github.io and was quite shocked. After code splitting and tree shaking I managed to get the total JS output size from 5.22MB down to 3.95MB, and the main entrypoint from 4.53MB down to 703KB.
The initial bundle was 5.22MB, with the main chunk 4.53MB (the red part). The only chunks split up were the different languages localizations.
One of the first things I noticed was that highlight.js included a bunch of languages, while I'm only using JSON. This eliminated 1.35MB.