Update README.md

Author: tbolis

README.md

@@ -57,7 +57,7 @@ Configuration Options
 | lineWidth         | Number                | 1             | The width of the line                                             | 
 | fillColor         | String                | transparent   | The fill color of the shape when applicable (e.g. circle)         |
 | undoSteps         | Number                | 15            | number of undo/redo steps to maintain                             |
-| imageFormat       | String                | png           | image format when calling toDataURL                               | 
+| imageFormat       | String                | png           | image format when calling toDataURL, can be png or jpeg           | 
 | scaleOnResize     | boolean               | false         | Scale the drawing when we resize the canvas                       |         
 | defaultData       | JSON or data URL      |               | Default initial data, can be json or URL data accroding to configuration option below, in the case of data URL the initial drawing will be improted as an image |
 | defaultDataType   | Enumeration (string)  | json          | The Type of initial data, can be either json or url               |