feat: use onClick handler on items rather than on root

[kentcdodds]

What: This swaps our document querying stuff from the root element with a more explicit onClick handler on the items.

Why: It probably should have always been this way...

How: Make the changes, see only one test broke, turns out that's unnecessary with the changes now so we can delete it.

Checklist:

• Documentation N/A
• Tests
• Ready to be merged
• Added myself to contributors table N/A

This should also make it easier to implement #185 👍

cc @gricard and @Swizec 😄

[codecov-io]

Codecov Report

Merging #192 into master will not change coverage.
The diff coverage is 100%.

@@          Coverage Diff          @@
##           master   #192   +/-   ##
=====================================
  Coverage     100%   100%           
=====================================
  Files           4      4           
  Lines         278    267   -11     
  Branches       65     61    -4     
=====================================
- Hits          278    267   -11

Impacted Files	Coverage Δ
src/downshift.js	100% <100%> (ø)	⬆️
src/utils.js	100% <100%> (ø)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 1b1fd1b...9112f86. Read the comment docs.

[tansongyang]

LGTM