fix(Dropdown): inserting char at a cursor position will the cursor to end

[layershifter]

Fixes #865.

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It's a known issue in Downshift, see:

• https://github.com/downshift-js/downshift#oninputvaluechange
• Cursor jumps to end of input when inputValue is a controlled prop downshift-js/downshift#217

Before

After

[codecov]

Codecov Report

Merging #897 into master will increase coverage by 0.02%.
The diff coverage is 33.33%.

@@            Coverage Diff             @@
##           master     #897      +/-   ##
==========================================
+ Coverage   80.57%   80.59%   +0.02%     
==========================================
  Files         648      648              
  Lines        8335     8334       -1     
  Branches     1485     1484       -1     
==========================================
+ Hits         6716     6717       +1     
+ Misses       1604     1602       -2     
  Partials       15       15

Impacted Files	Coverage Δ
...ackages/react/src/components/Dropdown/Dropdown.tsx	33.87% <33.33%> (+0.35%)	⬆️

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[silviuaavram]

like a charm. thanks a bunch!