add layout component with header, content, sider and footer

src/components/layout/content.vue

@@ -0,0 +1,28 @@
+<template>
+    <div :class="wrapClasses"><slot></slot></div>
+</template>
+<script>
+    const prefixCls = 'ivu-layout';
+    export default {
+        name: 'Content',
+        props: {
+            className: {
+                type: String,
+                default: ''
+            }
+        },
+        data () {
+            return {
+                prefixCls: prefixCls
+            };
+        },
+        computed: {
+            wrapClasses () {
+                return [
+                    `${prefixCls}-content`,
+                    this.className
+                ];
+            }
+        }
+    };
+</script>