Function chartRowXToDate : Opposite of chartRowDateToX

[ThibaultBarolat]

Is your feature request related to a problem? Please describe.
To add task or move task, I need to know where the user clicked/dropped. With click event, we can get the x position, but there is no simple way to get the corresponding Date from X.

Describe the solution you'd like
Implement a helper function which returns the Date from a X position (opposite of existing function chartRowDateToX).

Describe alternatives you've considered
I have considered to use a ratio between two dates and their chartRowDateToX but it doesn't take into account if we don't display the weekends.

Additional context
N/A