This property defines the border of the drawing area.
border: { width: Number, color: 'string' | JSON Object, dash: 'string' }
width: a number that defines the width of the border around the drawing area. The default value is zero (no border).
color: a color defined by a keyword or numerical specification string or a gradient defined by a string or JSON Object. The default value is transparent.
dash: a string that defines the border's dash style. The default value is '' (a solid line). Use a string of numbers that defines the width of a dash followed by the width of the gap between dashes (e.g., dash: '1 1' draws a dotted line).
border: { width: 4, color: 'red', dash: '4 2' }