update README.md

README.md

@@ -419,6 +419,9 @@ iframeCSSFileName : Name or Array of the CSS file to apply inside the iframe.
                     Applied by searching by filename in the link tag of document,
                     or put the URL value (".css" can be omitted).   default: 'suneditor' {Array|String}
                     ex) '.+' or ['suneditor', 'http://suneditor.com/sample/css/sample.css', '.+\\.min\\.css']
+previewTemplate : A template of the "preview".
+                  The {{contents}} part in the HTML string is replaced with the contents of the editor. default: null {String}
+                  ex) "<h1>Preview Template</h1> {{contents}} <div>_Footer_</div>"
 codeMirror      : If you put the CodeMirror object as an option, you can do Codeview using CodeMirror. default: null {Object}
                   Use version 5.x.x // https://github.com/codemirror/CodeMirror
                   ex) codeMirror: CodeMirror // Default option