Improvement: Chart selection point with custom string data representation on top instead of value

[dautovicharis]

v2 ticket

Ticket description:

I have started using this library in my project and wanted to extend ChartData class which for the result has more readable chart selection for the user in some cases.

This is currently done only for BarChartView because I’m using only this chart type, but I can easily apply the same logic for others charts.

Branch: https://github.com/dautovicharis/ChartView/tree/improvement/chart_data_class Commit: https://github.com/AppPear/ChartView/commit/69ebade2974ad673b78c71a812cd07b2a24d98e5

Video: https://streamable.com/7z2k1d

Please let me know if this improvement is worth it so I can create a Pull Request. Thanks