Add support for bar charts

Closes #103

docs/input/widgets/barchart.md

@@ -0,0 +1,75 @@
+Title: Bar Chart
+Order: 1
+---
+
+Use `BarChart` to render bar charts to the console.
+
+<img src="../assets/images/barchart.png" style="width: 100%;" />
+
+# Usage
+
+## Basic usage
+
+```csharp
+AnsiConsole.Render(new BarChart()
+    .Width(60)
+    .Label("[green bold underline]Number of fruits[/]")
+    .CenterLabel()
+    .AddItem("Apple", 12, Color.Yellow)
+    .AddItem("Orange", 54, Color.Green)
+    .AddItem("Banana", 33, Color.Red));
+```
+
+## Add items with converter
+
+```csharp
+// Create a list of fruits
+var items = new List<(string Label, double Value)>
+{
+    ("Apple", 12),
+    ("Orange", 54),
+    ("Banana", 33),
+};
+
+// Render bar chart
+AnsiConsole.Render(new BarChart()
+    .Width(60)
+    .Label("[green bold underline]Number of fruits[/]")
+    .CenterLabel()
+    .AddItems(items, (item) => new BarChartItem(
+        item.Label, item.Value, Color.Yellow)));
+```
+
+## Add items implementing IBarChartItem
+
+```csharp
+public sealed class Fruit : IBarChartItem
+{
+    public string Label { get; set; }
+    public double Value { get; set; }
+    public Color? Color { get; set; }
+
+    public Fruit(string label, double value, Color? color = null)
+    {
+        Label = label;
+        Value = value;
+        Color = color;
+    }
+}
+
+// Create a list of fruits
+var items = new List<Fruit>
+{
+    new Fruit("Apple", 12, Color.Yellow),
+    new Fruit("Orange", 54, Color.Red),
+    new Fruit("Banana", 33, Color.Green),
+};
+
+// Render bar chart
+AnsiConsole.Render(new BarChart()
+    .Width(60)
+    .Label("[green bold underline]Number of fruits[/]")
+    .CenterLabel()
+    .AddItem(new Fruit("Mango", 3))
+    .AddItems(items));
+```