Only list font names once

src/main.rs

@@ -1255,9 +1255,11 @@ impl Application for App {
                         .families
                         .first()
                         .map_or_else(|| face.post_script_name.to_string(), |x| x.0.to_string());
+                    if !font_names.contains(&font_name) {
                         font_names.push(font_name);
                     }
                 }
+            }
             font_names.sort();
             font_names
         };