feat(event): add item-changed event

[darrenjennings]

Fixes #177

[codecov-io]

Codecov Report

Merging #182 into master will increase coverage by 0.08%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #182      +/-   ##
==========================================
+ Coverage   84.70%   84.79%   +0.08%     
==========================================
  Files           1        1              
  Lines         170      171       +1     
  Branches       49       49              
==========================================
+ Hits          144      145       +1     
  Misses         11       11              
  Partials       15       15              

Impacted Files	Coverage Δ
src/Autosuggest.vue	84.79% <100.00%> (+0.08%)	⬆️

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