Fix qax-os#482, font strike style support

Author: xuri

excelize_test.go

@@ -775,7 +775,7 @@ func TestSetCellStyleFont(t *testing.T) {
 
 	assert.NoError(t, f.SetCellStyle("Sheet2", "A4", "A4", style))
 
-	style, err = f.NewStyle(`{"font":{"color":"#777777"}}`)
+	style, err = f.NewStyle(`{"font":{"color":"#777777","strike":true}}`)
 	if !assert.NoError(t, err) {
 		t.FailNow()
 	}

styles.go

@@ -1993,6 +1993,10 @@ func (f *File) setFont(formatStyle *formatStyle) *xlsxFont {
 	if fnt.Name.Val == "" {
 		fnt.Name.Val = f.GetDefaultFont()
 	}
+	if formatStyle.Font.Strike {
+		strike := true
+		fnt.Strike = &strike
+	}
 	val, ok := fontUnderlineType[formatStyle.Font.Underline]
 	if ok {
 		fnt.U = &attrValString{Val: val}

xmlStyles.go

@@ -320,6 +320,7 @@ type formatFont struct {
 	Underline string  `json:"underline"`
 	Family    string  `json:"family"`
 	Size      float64 `json:"size"`
+	Strike    bool    `json:"strike"`
 	Color     string  `json:"color"`
 }