Add isMinValueAtCenter property to RadarChartData

[soraef]

Summary

This PR adds the isMinValueAtCenter flag to the RadarChartPainter class to allow the minimum value to be centered in the RadarChart.

Related Issues

• Fixes Radar plot center point is zero #1351
• Fixes How can I set the center point to 0, fix the maximum value to 100, and not require my data to include the maximum value? #1442

Changes

• Added isMinValueAtCenter flag to RadarChartData
• Updated RadarChartPainter methods to support centering the minimum value when isMinValueAtCenter is true

isMinValueAtCenter Comparison

isMinValueAtCenter is false	isMinValueAtCenter is true

[soraef]

Thank you for the wonderful product. I use it all the time.

After implementing the changes, I realized that the isMinValueAtCenter flag might not be necessary. Should the minimum value be centered by default? If the current behavior is a bug, it would be better to make the minimum value centered by default instead of adding a flag. This would simplify the code and avoid unnecessary complexity.

[imaNNeo]

Yes I think it is a bug and it should always be centered