Window scroller types

[TrySound]

First PR with distributable types.

[codecov-io]

Codecov Report

Merging #915 into master will decrease coverage by 0.1%.
The diff coverage is 91.66%.

@@            Coverage Diff            @@
##           master    #915      +/-   ##
=========================================
- Coverage   90.01%   89.9%   -0.11%     
=========================================
  Files          57      57              
  Lines        1612    1615       +3     
=========================================
+ Hits         1451    1452       +1     
- Misses        161     163       +2

Impacted Files	Coverage Δ
source/WindowScroller/index.js	0% <0%> (ø)	⬆️
source/WindowScroller/utils/dimensions.js	100% <100%> (ø)	⬆️
source/WindowScroller/utils/onScroll.js	97.05% <85.71%> (-2.95%)	⬇️
source/WindowScroller/WindowScroller.js	86.27% <95.45%> (-0.52%)	⬇️

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