优化layout样式

src/components/layout/index.tsx

@@ -10,7 +10,8 @@ const headerStyle: React.CSSProperties = {
   height: 'auto',
   background: 'none',
   padding: 0,
-  lineHeight: '1'
+  lineHeight: '1',
+  position: 'relative'
 };
 
 const contentStyle: React.CSSProperties = {
@@ -18,13 +19,15 @@ const contentStyle: React.CSSProperties = {
   lineHeight: '1',
   color: '',
   backgroundColor: '',
+  position: 'relative',
 };
 
 const footerStyle: React.CSSProperties = {
   color: '',
   backgroundColor: '',
   lineHeight: '1',
-  padding: 0
+  padding: 0,
+  position: 'relative'
 };
 
 type Props = {