v0.7-alpha

1. First-ever Null Safety Release.
2. Chart Implemented with much better visuality as compared to previous.
3. Added one more indicator (Chart)
4. removed extra buttons and integrated their functionality in Toogle Buttons (Chart)
5. Added Some new Buttons with Extra Functionality (Chart)
6. Replaced Date Range Picker with Flutters own one- Old DateRangePicker was not compatible with Null Safety.