FreehandRoi Tool
How to set up the FreehandRoi tool:
// Init cornerstone tools
cornerstoneTools.init();
// Enable any elements, and display images
// ...
// Add our tool, and set it's mode
const FreehandRoiTool = cornerstoneTools.FreehandRoiTool;
cornerstoneTools.addTool(FreehandRoiTool)
cornerstoneTools.setToolActive('FreehandRoi', { mouseButtonMask: 1 })