:sparkles: 增加单个参数的 orderByAsc/orderByDesc

虽然并没有解决问题，但大部分情况下排序参数都只有一个，这样足够覆盖大部分情况了
Fix #720

mybatis-plus-core/src/main/java/com/baomidou/mybatisplus/core/conditions/interfaces/Func.java

@@ -298,6 +298,13 @@ public interface Func<Children, R> extends Serializable {
      */
     Children groupBy(boolean condition, R... columns);
 
+    /**
+     * ignore
+     */
+    default Children orderByAsc(R column) {
+        return orderByAsc(true, column);
+    }
+
     /**
      * ignore
      */
@@ -317,6 +324,13 @@ public interface Func<Children, R> extends Serializable {
         return orderBy(condition, true, columns);
     }
 
+    /**
+     * ignore
+     */
+    default Children orderByDesc(R column) {
+        return orderByDesc(true, column);
+    }
+
     /**
      * ignore
      */