feat(barchar): add BarChart::grouped constructor (#1513)

Add a new constructor to the `BarChart` widget that allows creating a
grouped barchart with multiple groups of bars.

Also add a new constructor to the `BarGroup` widget that allows creating
a group of bars with a label.

ratatui-widgets/src/barchart.rs

@@ -172,6 +172,31 @@ impl<'a> BarChart<'a> {
         }
     }
 
+    /// Creates a new `BarChart` widget with a group of bars.
+    ///
+    /// # Examples
+    ///
+    /// ```rust
+    /// use ratatui::widgets::{Bar, BarChart, BarGroup};
+    ///
+    /// BarChart::grouped(vec![
+    ///     BarGroup::with_label(
+    ///         "Group 1",
+    ///         vec![Bar::with_label("A", 10), Bar::with_label("B", 20)],
+    ///     ),
+    ///     BarGroup::with_label(
+    ///         "Group 2",
+    ///         [Bar::with_label("C", 30), Bar::with_label("D", 40)],
+    ///     ),
+    /// ]);
+    /// ```
+    pub fn grouped<T: Into<Vec<BarGroup<'a>>>>(groups: T) -> Self {
+        Self {
+            data: groups.into(),
+            ..Default::default()
+        }
+    }
+
     /// Add group of bars to the `BarChart`
     ///
     /// # Examples

ratatui-widgets/src/barchart/bar_group.rs

@@ -43,6 +43,26 @@ impl<'a> BarGroup<'a> {
         }
     }
 
+    /// Creates a new `BarGroup` with the given bars and label.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use ratatui::style::{Style, Stylize};
+    /// use ratatui::widgets::{Bar, BarGroup};
+    ///
+    /// let group = BarGroup::with_label(
+    ///     "Group1",
+    ///     vec![Bar::with_label("A", 10), Bar::with_label("B", 20)],
+    /// );
+    /// ```
+    pub fn with_label<T: Into<Line<'a>>, B: Into<Vec<Bar<'a>>>>(label: T, bars: B) -> Self {
+        Self {
+            label: Some(label.into()),
+            bars: bars.into(),
+        }
+    }
+
     /// Set the group label
     ///
     /// `label` can be a [`&str`], [`String`] or anything that can be converted into [`Line`].