feat: add JavaScript learning section with starter lessons and sidebar section headers

Implementation following plan:
- S01: Foundation: schema, section config, and router
- S02: Install CodeMirror JavaScript language support
- S03: Create JavaScript lesson JSON files (variables, DOM, events)
- S04: Register JavaScript lessons in module stores
- S05: Add JavaScript validation logic
- S06: Add JavaScript mode to LessonEngine preview rendering
- S07: Add JavaScript mode to CodeEditor
- S08: Update app.js for JavaScript mode support
- S09: Update navigation HTML and CSS theming for JavaScript section
- S10: Add section grouping headers in sidebar navigation
- S11: Update and write tests

src/config/sections.js

@@ -31,6 +31,13 @@ export const sections = {
 		description: "Lightweight markup language for formatting text",
 		color: "#5b8dd9",
 		order: 4
+	},
+	javascript: {
+		id: "javascript",
+		title: "JavaScript",
+		description: "Interactive scripting for web pages",
+		color: "#f0db4f",
+		order: 5
 	}
 };
 
@@ -65,6 +72,7 @@ export function getModuleSection(module) {
 	if (mode === "html") return "html";
 	if (mode === "tailwind") return "tailwind";
 	if (mode === "markdown") return "markdown";
+	if (mode === "javascript") return "javascript";
 	return "css";
 }