v3.9.0

New feature

export SVG charts into PNG/JPEG #134

// method by default generates PNG image
chart.exportImage();

// if quality provided then JPEG is generated
// quality - a number between 0 to 1 indicating image quality (quality = 0 generates PNG image)
// bgcolor - a string value for background color, any valid CSS color value (defaults to '#fff')
chart.exportImage({ quality: 1, bgcolor: 'blue' });