[Feature Request]: PieChart with exploding sections

# Description

Highlighting a section by "exploding" it (or in other words sliding it outwards from the center) with smooth animations could add to the UX and add a new level of design possibilities for PieCharts.

# Example

# Proposed Solution

```dart
class PieChartSectionData {
// ...
final double sectionOffset;
// ...
}

class PieChartPainter {
// ...
void drawSections(...) {
final section = data.sections[i];
if (section.value == 0) {
continue;
}
final sectionDegree = sectionsAngle[i];

// Compute offset for "exploded" sections
final sectionCenterAngle = tempAngle + (sectionDegree / 2);
final sectionOffset = section.sectionOffset;
final offsetDx =
math.cos(Utils().radians(sectionCenterAngle)) * sectionOffset;
final offsetDy =
math.sin(Utils().radians(sectionCenterAngle)) * sectionOffset;
final sectionCenter = center.translate(offsetDx, offsetDy);
// ...
}
}
```

Start by locating PieChartSectionData and PieChartPainter.drawSections, then read how section angles and centers are currently calculated. Implement the proposed section offset behavior and smooth animations for exploded sections, and verify that PieChart examples or existing chart tests show sections moving outward without disrupting other sections.

Written by the indexing model from the issue text.