[style] add enum for text alignment

src/style.rs

@@ -40,6 +40,13 @@ pub enum Modifier {
     Underline,
 }
 
+#[derive(Debug, Clone, Copy, PartialEq)]
+pub enum Alignment {
+    Left,
+    Center,
+    Right,
+}
+
 #[derive(Debug, Clone, Copy, PartialEq)]
 pub struct Style {
     pub fg: Color,