Add default protectedCss. Closes #131

src/editor/config/config.js

@@ -38,7 +38,7 @@ module.exports = {
   width: '100%',
 
   // CSS that could only be seen (for instance, inside the code viewer)
-  protectedCss: '',
+  protectedCss: '*{box-sizing: border-box;} body{margin: 0;}',
 
   // CSS for the iframe which containing the canvas, useful if you need to custom something inside
   // (eg. the style of the selected component)