feat: Add Freehand as a default available tool (#21)

* adding Freehand to default availableTool

* adding Freehand to default availableTool 2

* Changing the name to �FreehandMouse

Author: MathisGuilhin

src/CornerstoneViewport/CornerstoneViewport.js

@@ -73,6 +73,7 @@ class CornerstoneViewport extends Component {
       { name: 'Wwwc', mouseButtonMasks: [1] },
       { name: 'Bidirectional', mouseButtonMasks: [1] },
       { name: 'Length', mouseButtonMasks: [1] },
+	    { name: 'FreehandMouse', mouseButtonMasks: [1] },
       { name: 'Angle', mouseButtonMasks: [1] },
       { name: 'StackScroll', mouseButtonMasks: [1] },
       { name: 'Brush', mouseButtonMasks: [1] },