Add docs for Legend options of chart

Author: xuri

chart.go

@@ -765,6 +765,7 @@ func (opts *Chart) parseTitle() {
 //	Categories
 //	Values
 //	Fill
+//	Legend
 //	Line
 //	Marker
 //	DataLabel
@@ -787,7 +788,10 @@ func (opts *Chart) parseTitle() {
 // optional and the default value was same with 'Values'.
 //
 // Fill: This set the format for the data series fill. The 'Fill' property is
-// optional
+// optional.
+//
+// Legend: This set the font of legend text for a data series. The 'Legend'
+// property is optional.
 //
 // Line: This sets the line format of the line chart. The 'Line' property is
 // optional and if it isn't supplied it will default style. The options that
@@ -1014,6 +1018,9 @@ func (opts *Chart) parseTitle() {
 // Set chart size by 'Dimension' property. The 'Dimension' property is optional.
 // The default width is 480, and height is 260.
 //
+// Set chart legend for all data series by 'Legend' property. The 'Legend'
+// property is optional.
+//
 // Set the bubble size in all data series for the bubble chart or 3D bubble
 // chart by 'BubbleSizes' property. The 'BubbleSizes' property is optional. The
 // default width is 100, and the value should be great than 0 and less or equal

chart_test.go

@@ -171,7 +171,8 @@ func TestAddChart(t *testing.T) {
 					Width: 1,
 				},
 			},
-			Legend: ChartLegend{Font: &Font{Family: "Arial", Size: 11, Strike: true, Color: "777777"}}},
+			Legend: ChartLegend{Font: &Font{Family: "Arial", Size: 11, Strike: true, Color: "777777"}},
+		},
 	}
 	series2 := []ChartSeries{
 		{