Updated Create canvas (markdown)

SVG-canvases.md

@@ -32,4 +32,39 @@ if (SVG.supported) {
 } else {
   alert('SVG not supported')
 }
-```
+```
+
+## ViewBox
+
+The `viewBox` attribute of an `<svg>` element can be managed with the `viewbox()` method. When supplied with arguments it will act as a setter:
+
+```javascript
+draw.viewbox(0, 0, 297, 210)
+```
+
+Without any attributes an instance of `SVG.ViewBox` will be returned:
+
+```javascript
+var box = draw.viewbox()
+```
+
+But the best thing about the `viewbox()` method is that you can get the zoom of the viewbox:
+
+```javascript
+var box = draw.viewbox()
+var zoom = box.zoom
+```
+
+If the size of the viewbox equals the size of the svg canvas, the zoom value will be 1.
+
+## Nested svg
+With this feature you can nest svg documents within each other. Nested svg documents have exactly the same features as the main, top-level svg document:
+
+```javascript
+var nested = draw.nested()
+
+var rect = nested.rect(200, 200)
+```
+
+
+_This functionality requires the nested.js module which is included in the default distribution._