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

.pi/skills/demo/README.md

@@ -18,6 +18,14 @@ showboat --help
 rodney --help
 ```
 
+### Rodney Chrome data directory
+
+Rodney needs write access to the Chrome data directory at `~/.rodney`. If you get `Permission denied` errors when running `rodney start`, fix it:
+
+```bash
+mkdir -p ~/.rodney && chmod 755 ~/.rodney
+```
+
 ## Usage
 
 In pi, invoke via: