Add highlight.js syntax highlighting to source viewer

- Install highlight.js via npm with 8 language definitions
- SourceViewer hook applies syntax highlighting on mount/update
- Atom One Dark theme for dark mode, Atom One Light for light mode
- Add hooks directory, package.json, and package-lock.json
- Add demo document and screenshots
- Add rodney-docker.md documentation
- Ignore .rodney/ chrome data directory

.gitignore

@@ -6,3 +6,5 @@ app/priv/blog/engineering/2026/04-24-what-it-takes-to-get-started-with-the-pi-co
 /tmp_work/
 .yaks
 transcripts/
+.pi/skills/demo/chrome
+.rodney/