add styleTags to the deep dive documentation

ref summernote/summernote#2946

Author: JosefAssad

01-deep-dive.md

@@ -152,6 +152,33 @@ $('#summernote').summernote({
 });
 {% endhighlight %}
 
+### Custom styles
+
+You can set your own selection of styles with the `styleTags` option.
+
+{% highlight javascript %}
+$('#summernote').summernote({
+  styleTags: [
+    'p',
+        { title: 'Blockquote', tag: 'blockquote', className: 'blockquote', value: 'blockquote' },
+        'pre', 'h1', 'h2', 'h3', 'h4', 'h5', 'h6'
+	],
+  });
+{% endhighlight %}
+
+The tags can be specified just by tag name (as with `p` or `pre` or `h1`-`h6` above). It is also
+possible to customize the style in more defaul by providing an object looking like:
+
+{% highlight javascript %}
+{
+     tag : 'tag name ',
+     title : 'dropdown item title',
+     style : 'dropdown item style',
+     className : 'applyed element class name and dropdown item className',
+     value : 'Value to apply when clicked'
+}
+{% endhighlight %}
+
 ### Custom fontNames
 You can define fontNames items with the `fontNames` option.