Add element visibility to calculations

[jalal246]

• Remove text selection from the entire document when starting dragging.
• Remove unnecessary getOffset method from core-instance.
• Add ability to reset DOMRect from outside the core-instance.
• core-instance accepts opts now.
• Add custom dataset data-index which refers to element order inside rendering list after the transform is calculated. We have now original order in the DOM tree and a transformation order related to elements' appearance on the screen.
• Introduce element visibility which is true when the element is visible on the viewport.
  • Calculate element visibility with scrolling.
  • Update element position in the store but don't transform when the element is hidden.
  • Invoke transformer when the element is visible,. Which is done with scrolling.
  • Scroll is throttled to the animated frame.
  • Add visibility exceptions to enhance UX. Immediate elements before and after the visible elements are isVisible: true
  • Done with adding new methods:
    • Inside the store:
      setViewport
setScrollXY
initELmIndicator
isElementHiddenInViewport
updateRegisteredLayoutIndicators
  • Inside the core-instance:
    visibilityHasChanged
• Refactor Jest Snapshots to include the new changes.