0.55.0

• FEATURE (by @emelinepal): Add tooltipBorder property in [LineTouchTooltipData], [BarTouchTooltipData], [ScatterTouchTooltipData], #692.
• BUGFIX (by @imaNNeoFighT): Fix tooltip issue on negative bar charts, #978.
• IMPROVEMENT (by @imaNNeoFighT): Use Container to draw axis-based charts border.
• FEATURE (by @FlorianArnould) Add the ability to select the RadarChart shape (circle or polygon), #1047.
• BUGFIX (by @imaNNeoFighT): Fix LineChart titles problem with single FlSpot, #1053.
• FEATURE (by @FlorianArnould) Add the ability to rotate the RadarChar titles, #883.
• BREAKING (by @FlorianArnould) RadarChartData.getTitle have a new parameter angle and now returns a RadarChartTitle instead of a simple string. (Read our Migration Guide to learn more about it)