Added ?json=1 to the define doc. (codesandbox#550)

Author: robertheessels

packages/homepage/content/docs/2-importing.md

@@ -112,3 +112,11 @@ You can do the exact same steps for a POST request, but instead of a URL you'd s
 #### Example Sandbox
 
 <iframe src="https://codesandbox.io/embed/qzlp7nw34q?editorsize=70&fontsize=14&hidenavigation=1&runonclick=1" style="width:100%; height:500px; border:0; border-radius: 4px; overflow:hidden;" sandbox="allow-modals allow-forms allow-popups allow-scripts allow-same-origin"></iframe>
+
+### Define without render
+
+If you want to define a new sandbox without getting it rendered, you can add `?json=1` to the request. For instance `https://codesandbox.io/api/v1/sandboxes/define?json=1`. Instead of the render, the result will be json data providing you with the `id` of the new sandbox.
+
+This is useful, for instance, if you need to create a new sandbox programatically, so you can then embed it on your site (See Embed documentation).
+
+Both `get` and `post` requests are supported.