Feat/radar max value config

[artsooter]

hello ，This PR is aims to add this feature in #2002

Problem background

We encountered two problems in the issue.

• How to set the maximum value of the Radar Chart to a specified value.
• How to display the maximum tick value on the chart.

Solution

This PR introduces two new parameters to RadarChartData:

1. maxValue Parameter

RadarChartData( dataSets: myDataSets, maxValue: 100.0, // Set custom maximum value )

• Type: double? (optional)
• Default: null (uses data maximum)
• Purpose: Allows setting a custom maximum value instead of calculating from data

2. showMaxTick Parameter

RadarChartData( dataSets: myDataSets, showMaxTick: true, // Show maximum tick value )

• Type: bool
• Default: false (preserves existing behavior)
• Purpose: Controls whether the maximum tick is displayed on the chart

Result