Implement tab width config

src/config.rs

@@ -146,6 +146,7 @@ pub struct Config {
     pub font_size: u16,
     pub syntax_theme_dark: String,
     pub syntax_theme_light: String,
+    pub tab_width: u16,
     pub vim_bindings: bool,
     pub word_wrap: bool,
     pub keybinds: HashMap<KeyBind, Action>,
@@ -159,6 +160,7 @@ impl Default for Config {
             font_size: 14,
             syntax_theme_dark: "gruvbox-dark".to_string(),
             syntax_theme_light: "gruvbox-light".to_string(),
+            tab_width: 4,
             vim_bindings: false,
             word_wrap: false,
             keybinds: KeyBind::load(),