switch to pure ESM

[mohsinulhaq]

https://gist.github.com/sindresorhus/a39789f98801d908bbc7ff3ecc99d99c

[codecov[bot]]

Codecov Report

Attention: 2 lines in your changes are missing coverage. Please review.

Comparison is base (3381a5b) 89.72% compared to head (3ddecd6) 90.80%.

Files	Patch %	Lines
src/usePopperTooltip.ts	97.87%	1 Missing :warning:
src/utils.ts	85.71%	1 Missing :warning:

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #176      +/-   ##
==========================================
+ Coverage   89.72%   90.80%   +1.08%     
==========================================
  Files           2        4       +2     
  Lines         146      457     +311     
  Branches       47       68      +21     
==========================================
+ Hits          131      415     +284     
- Misses         15       42      +27     

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