Add the Italian version docs for the 3D cone column chart

it/SUMMARY.md

@@ -139,6 +139,7 @@
   * [Grafico a colonne 3D](chart/col3D.md)
   * [Istogramma in pila 3D](chart/col3DStacked.md)
   * [Istogramma in pila 3D al 100%](chart/col3DPercentStacked.md)
+  * [Istogramma a cono 3D](chart/col3DCone.md)
 * [Immagine](image.md)
   * [Aggiungi immagine](image.md#AddPicture)
   * [Ottieni immagine](image.md#GetPicture)

it/chart/col3DCone.md

@@ -0,0 +1,91 @@
+# Istogramma a cono 3D {#col3DCone}
+
+Ad esempio, aggiungi un istogramma a cono 3D come questo:
+
+<p align="center"><img width="770" src="../images/3d_cone_column_chart.png" alt="creare un istogramma a cono 3D con Excelize utilizzando Go"></p>
+
+```go
+package main
+
+import (
+    "fmt"
+
+    "github.com/xuri/excelize/v2"
+)
+
+func main() {
+    f := excelize.NewFile()
+    defer func() {
+        if err := f.Close(); err != nil {
+            fmt.Println(err)
+        }
+    }()
+    if err := f.SetSheetName("Sheet1", "Foglio1"); err != nil {
+        fmt.Println(err)
+        return
+    }
+    for idx, row := range [][]interface{}{
+        {nil, "Mela", "Arancia", "Pera"},
+        {"Piccolo", 2, 3, 3},
+        {"Normale", 5, 2, 4},
+        {"Grande", 6, 7, 8},
+    } {
+        cell, err := excelize.CoordinatesToCellName(1, idx+1)
+        if err != nil {
+            fmt.Println(err)
+            return
+        }
+        if err := f.SetSheetRow("Foglio1", cell, &row); err != nil {
+            fmt.Println(err)
+            return
+        }
+    }
+    if err := f.AddChart("Foglio1", "E1", &excelize.Chart{
+        Type: excelize.Col3DCone,
+        Series: []excelize.ChartSeries{
+            {
+                Name:       "Foglio1!$A$2",
+                Categories: "Foglio1!$B$1:$D$1",
+                Values:     "Foglio1!$B$2:$D$2",
+            },
+            {
+                Name:       "Foglio1!$A$3",
+                Categories: "Foglio1!$B$1:$D$1",
+                Values:     "Foglio1!$B$3:$D$3",
+            },
+            {
+                Name:       "Foglio1!$A$4",
+                Categories: "Foglio1!$B$1:$D$1",
+                Values:     "Foglio1!$B$4:$D$4",
+            },
+        },
+        Format: excelize.GraphicOptions{
+            OffsetX: 15,
+            OffsetY: 10,
+        },
+        Legend: excelize.ChartLegend{
+            Position: "left",
+        },
+        Title: []excelize.RichTextRun{
+            {
+                Text: "Grafico a colonne a cono 3D",
+            },
+        },
+        PlotArea: excelize.ChartPlotArea{
+            ShowCatName:     false,
+            ShowLeaderLines: false,
+            ShowPercent:     true,
+            ShowSerName:     true,
+            ShowVal:         true,
+        },
+        ShowBlanksAs: "zero",
+    }); err != nil {
+        fmt.Println(err)
+        return
+    }
+    // Salva cartella di lavoro
+    if err := f.SaveAs("Cartel1.xlsx"); err != nil {
+        fmt.Println(err)
+    }
+}
+```