Export enum ALIGNMENT as scrollAlignment to use with scrollToAlignment

[mts]

This PR offers a solution to the following issue: https://github.com/clauderic/react-tiny-virtual-list/issues/68

[codecov[bot]]

Codecov Report

Merging #69 into master will not change coverage. The diff coverage is 100%.

@@           Coverage Diff           @@
##           master      #69   +/-   ##
=======================================
  Coverage   94.28%   94.28%           
=======================================
  Files           3        3           
  Lines         140      140           
  Branches       17       17           
=======================================
  Hits          132      132           
  Misses          8        8

Impacted Files	Coverage Δ
src/index.tsx	100% <100%> (ø)	:arrow_up:

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[stephenotalora]

@clauderic fyi***