feat: UIFont extension 추가

- preferred font를 확장하여 bold, italic을 손쉽게 적용할 수 있도록 extension 마련

iOS/Projects/Shared/DesignSystem/Sources/UIButtonConfiguration+MainCircular.swift

@@ -72,12 +72,7 @@ public extension UIButton.Configuration {
       default: break
       }
       button.configuration?.title = text
-      button.configuration?.font = UIFont(
-        descriptor: UIFont
-          .preferredFont(forTextStyle: .largeTitle)
-          .fontDescriptor.withSymbolicTraits(.traitBold)!,
-        size: 0
-      )
+      button.configuration?.font = .preferredFont(forTextStyle: .largeTitle, with: .traitBold)
     }
   }
 }

iOS/Projects/Shared/DesignSystem/Sources/UIFont+preferredFont.swift

@@ -0,0 +1,20 @@
+//
+//  UIFont+preferredFont.swift
+//  DesignSystem
+//
+//  Created by 홍승현 on 11/14/23.
+//  Copyright © 2023 kr.codesquad.boostcamp8. All rights reserved.
+//
+
+import UIKit
+
+public extension UIFont {
+  static func preferredFont(forTextStyle: TextStyle, with traits: UIFontDescriptor.SymbolicTraits) -> UIFont {
+    let font = Self.preferredFont(forTextStyle: forTextStyle)
+    guard let descriptor = font.fontDescriptor.withSymbolicTraits(traits) else {
+      return font
+    }
+
+    return UIFont(descriptor: descriptor, size: 0)
+  }
+}