fix: remove undefined crossterm attributes in windows builds

src/backend/crossterm.rs

@@ -108,6 +108,7 @@ impl From<Color> for Option<crossterm::Color> {
 }
 
 impl From<Modifier> for Option<crossterm::Attribute> {
+    #[cfg(unix)]
     fn from(modifier: Modifier) -> Option<crossterm::Attribute> {
         match modifier {
             Modifier::Blink => Some(crossterm::Attribute::SlowBlink),
@@ -120,4 +121,13 @@ impl From<Modifier> for Option<crossterm::Attribute> {
             _ => None,
         }
     }
+
+    #[cfg(windows)]
+    fn from(modifier: Modifier) -> Option<crossterm::Attribute> {
+        match modifier {
+            Modifier::Bold => Some(crossterm::Attribute::Bold),
+            Modifier::Underline => Some(crossterm::Attribute::Underlined),
+            _ => None,
+        }
+    }
 }