Fix Calendar Alignment on Mobile

[bharath6365]

Description

Fixed the logic that decided the number of months that had to be rendered on mobile. Previously it was rendering 4. We have space only to render 1.

Related issues

#71

Impacted Areas in the application

Date Picker

[vercel]

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[ivan-aksamentov]

Thanks @bharath6365!

Could you please also investigate how it looks on iPad emulator in Chrome?
In particular, regarding the withPortal option of DateRangePicker. For some reason portal rendering is activated on iPad, but not in iPhone X, for example.

Could we avoid hardcoding number of months at all?

I found this storybook to be useful to explore the options:
https://airbnb.io/react-dates

Don't hesitate also if you think that there is a better option than react-dates we can replace it then.