v2.5.0

• Upgrade webview_flutter to 4.2.4
• Upgrade Echarts to 5.4.3
• Upgrade SDK to >=2.12.0 <4.0.0

v2.4.0

• Upgrade webview_flutter to 3.0.4
• Upgrade Echarts to 5.3.3
• Set chart widget's background color to transparent, and remove workarounds.