ChatRoom 문자열 리소스화

app/src/main/res/layout/fragment_chat_background_picker.xml

@@ -20,7 +20,7 @@
             android:id="@+id/iv_close"
             android:layout_width="24dp"
             android:layout_height="24dp"
-            android:contentDescription="닫기"
+            android:contentDescription="@string/a11y_close"
             android:src="@drawable/ic_back" />
 
         <TextView
@@ -32,7 +32,7 @@
             android:ellipsize="end"
             android:fontFamily="@font/pretendard_bold"
             android:maxLines="1"
-            android:text="배경 이미지 선택"
+            android:text="@string/chat_background_picker_title"
             android:textColor="#FFFFFFFF"
             android:textSize="20sp" />
     </LinearLayout>