design: Column mode auto padding

lib/views/widgets/max_width_body.dart

@@ -0,0 +1,38 @@
+import 'dart:math';
+
+import 'package:flutter/material.dart';
+
+class MaxWidthBody extends StatelessWidget {
+  final Widget child;
+  final double maxWidth;
+  final bool withScrolling;
+
+  const MaxWidthBody({
+    this.child,
+    this.maxWidth = 600,
+    this.withScrolling = false,
+    Key key,
+  }) : super(key: key);
+  @override
+  Widget build(BuildContext context) {
+    return LayoutBuilder(
+      builder: (context, constraints) {
+        final padding = EdgeInsets.symmetric(
+          horizontal: max(0, (constraints.maxWidth - maxWidth) / 2),
+        );
+        return withScrolling
+            ? SingleChildScrollView(
+                physics: ScrollPhysics(),
+                child: Padding(
+                  padding: padding,
+                  child: child,
+                ),
+              )
+            : Padding(
+                padding: padding,
+                child: child,
+              );
+      },
+    );
+  }
+}