Feat: continue refactoring

crates/markdown/src/highlighter.rs

@@ -0,0 +1,13 @@
+use ratatui::style::Style;
+
+pub trait CodeHighlighter {
+    fn highlight(&self, line: &str) -> Vec<(Style, String)>;
+}
+
+pub struct NoHighlight;
+
+impl CodeHighlighter for NoHighlight {
+    fn highlight(&self, line: &str) -> Vec<(Style, String)> {
+        vec![(Style::default(), line.to_string())]
+    }
+}