feat: add Markdown learning module with 8 beginner lessons

- Add markdown-basics module with lessons for headings, text formatting,
  lists, links, and inline code
- Integrate markdown section with blue color theme (#5b8dd9)
- Add markdown mode support in CodeEditor and LessonEngine
- Add markdown preview rendering using marked library
- Add section overview page with educational content
- Add markdown reference page with syntax guide
- Add i18n translations for 6 languages (EN, DE, PL, ES, AR, UK)
- Update router to recognize #markdown as section route
- Add all section-specific CSS styles for markdown theme

src/config/sections.js

@@ -24,6 +24,13 @@ export const sections = {
 		description: "Utility-first CSS framework",
 		color: "#26a69a",
 		order: 3
+	},
+	markdown: {
+		id: "markdown",
+		title: "Markdown",
+		description: "Lightweight markup language for formatting text",
+		color: "#5b8dd9",
+		order: 4
 	}
 };
 
@@ -57,6 +64,7 @@ export function getModuleSection(module) {
 	const mode = module.mode || "css";
 	if (mode === "html") return "html";
 	if (mode === "tailwind") return "tailwind";
+	if (mode === "markdown") return "markdown";
 	return "css";
 }