Сlipped chart when zoomed maximum or shifted with onPan event

[kalitsinskiy]

In case when the chart is maximum zoomed or shifted with onPan event some sides data points disappear due filtering data logic.
I fount out the solution way, just add on extra data point from both side to avoid case when chart looks like clipped, it fixs this issue and not so much impact on perfomance.
My production project is very dependent on this package, so I will be very grateful approvement PR in comments below, because as for now I have cloned the package to the repository and manually fixed this issue.

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