fix: fireEvent in IE11

[eps1lon]

Fixes #421
What:

Use createEvent instead of new Event if Event is not constructable

Why:

new Event is not supported in IE 11

How:

Use https://developer.mozilla.org/en-US/docs/Web/API/CustomEvent/CustomEvent#Polyfill

Checklist:

• ~[ ] Documentation added to the
  docs site
• [ ] I've prepared a PR for types targeting
  DefinitelyTyped~
• Tests: Verified pass in https://github.com/eps1lon/ie-fire-event-repro/runs/421197374?check_suite_focus=true using the codesandbox build via ysgk/ie-fire-event-repro@master...eps1lon:fix/ie11-events
• Ready to be merged
  

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[codecov]

Codecov Report

Merging #445 into master will not change coverage.
The diff coverage is 100%.

@@          Coverage Diff          @@
##           master   #445   +/-   ##
=====================================
  Coverage     100%   100%           
=====================================
  Files          22     22           
  Lines         384    385    +1     
  Branches       90     91    +1     
=====================================
+ Hits          384    385    +1

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

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[kentcdodds]

Looks good to me 👍

[kentcdodds]

🎉 This PR is included in version 6.12.2 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

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