feat: add locale const & lcid infos

cell.go

@@ -1372,7 +1372,7 @@ func (f *File) formattedValue(c *xlsxC, raw bool, cellType CellType) (string, er
 func (f *File) getBuiltInNumFmtCode(numFmtId int) string {
 	locale := ""
 	if f.options != nil {
-		locale = f.options.Locale
+		locale = strings.ToLower(string(f.options.Locale))
 	}
 	numFmtCode := builtInNumFmt[numFmtId]
 	if locale == "" {

cell_test.go

@@ -877,23 +877,6 @@ func TestFormattedValue(t *testing.T) {
 		assert.Equal(t, "0_0", fn("0_0", "", false, CellTypeNumber))
 	}
 
-	// Test format value with built-in number format ID = 14
-	styleID, err = f.NewStyle(&Style{
-		NumFmt: 14,
-	})
-	assert.NoError(t, err)
-	result, err = f.formattedValue(&xlsxC{S: styleID, V: "43528"}, false, CellTypeNumber)
-	assert.NoError(t, err)
-	assert.Equal(t, "03-04-19", result)
-	originalFileOptions := f.options
-	f.options = &Options{
-		Locale: "zh-cn",
-	}
-	result, err = f.formattedValue(&xlsxC{S: styleID, V: "43528"}, false, CellTypeNumber)
-	assert.NoError(t, err)
-	assert.Equal(t, "2019/3/4", result)
-	f.options = originalFileOptions
-
 	// Test format value with built-in number format zh-cn
 	styleID31, err := f.NewStyle(&Style{
 		NumFmt: 31,
@@ -905,9 +888,9 @@ func TestFormattedValue(t *testing.T) {
 		Lang:   "zh-cn",
 	})
 	assert.NoError(t, err)
-	originalFileOptions = f.options
+	originalFileOptions := f.options
 	f.options = &Options{
-		Locale: "zh-cn",
+		Locale: ZH_CN,
 	}
 	result, err = f.formattedValue(&xlsxC{S: styleID31, V: "43528"}, false, CellTypeNumber)
 	assert.NoError(t, err)

excelize.go

@@ -88,7 +88,7 @@ type Options struct {
 	RawCellValue      bool
 	UnzipSizeLimit    int64
 	UnzipXMLSizeLimit int64
-	Locale            string
+	Locale            Locale
 }
 
 // OpenFile take the name of an spreadsheet file and returns a populated