[Calendar]: provide property "useVerticalSliders" for easier access to scroll to months

• enhancement
• Framework7 Version: 2

Actually, Calendar-Component (https://framework7.io/docs/calendar.html) has two short sliders for month and years above at the top. When user wants to jump easily to month august and the actual month in the slider is january. Then he must click 7 times (!) the slider for the month - this is tedious.. This can be improved by having a property ("useVerticalSliders"), so that each compnent "month", "year" and "days" are displayed vertically. With this, "year" and "month" has more space and the slider for it can be expanded:

Both, month-scroller (at the bottom), and days-scroller stays in sync while scrolling.

With this, user does not need to make clicks, only scrolls.

Start with the Calendar component documentation at https://framework7.io/docs/calendar.html and inspect the existing month, year, and day scrollers. Define how a useVerticalSliders property should arrange these components and keep the month and day scrollers synchronized. Done means users can scroll vertically to reach months and years without repeated clicks.