Implement line numbers

src/config.rs

@@ -150,6 +150,7 @@ pub struct Config {
     pub auto_indent: bool,
     pub font_name: String,
     pub font_size: u16,
+    pub line_numbers: bool,
     pub syntax_theme_dark: String,
     pub syntax_theme_light: String,
     pub tab_width: u16,
@@ -165,6 +166,7 @@ impl Default for Config {
             auto_indent: true,
             font_name: "Fira Mono".to_string(),
             font_size: 14,
+            line_numbers: true,
             syntax_theme_dark: "gruvbox-dark".to_string(),
             syntax_theme_light: "gruvbox-light".to_string(),
             tab_width: 4,