feat: start to scroll when an event is dragged out of the visible area

[RobertMischke]

What changed: On the the day view, when events are dragged outside of the view, the view port starts scrolling. It is not perfect...

The following problems exist:

• the scrolling stops, after a certain amount of jumps, probably because the dragMove() event does not fire anymore
• it is possible to drag the event out of view.

[codecov-io]

Codecov Report

Merging #909 into 0.27 will decrease coverage by 0.08%.
The diff coverage is 93.33%.

@@            Coverage Diff            @@
##             0.27    #909      +/-   ##
=========================================
- Coverage   98.19%   98.1%   -0.09%     
=========================================
  Files          38      39       +1     
  Lines         829     843      +14     
  Branches       64      64              
=========================================
+ Hits          814     827      +13     
- Misses          0       1       +1     
  Partials       15      15

Impacted Files	Coverage Δ
...dar/src/modules/day/calendar-day-view.component.ts	99.13% <100%> (+0.02%)	⬆️
...lendar/src/modules/day/calendar-day-auto-scroll.ts	90.9% <90.9%> (ø)

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[mattlewis92]

Hey, thanks for opening this PR! I think it's better to solve it in the drag and drop lib directly though so then it will work on all 3 views, plus anyone else that uses that library.

Thankfully, there is already a package which does most of the heavy lifting, integrating it should be a case of calling autoScroll when the drag starts and then destroying the scroll listener when the drag ends.

Would you like to take a go at a PR to add it over at the angular-draggable-droppable repo?

[mattlewis92]

Thanks for your contribution, I just released 0.27.5 which now supports scrolling the container when dragging events 😄