Update typescript definitions to support node16 mode.

[jefbarn]

Fixes #25

[codecov]

Codecov Report

Merging #26 (1dcae55) into master (76b388c) will not change coverage.
Report is 1 commits behind head on master.
The diff coverage is n/a.

❗ Current head 1dcae55 differs from pull request most recent head d28d619. Consider uploading reports for the commit d28d619 to get more accurate results

@@           Coverage Diff           @@
##           master      #26   +/-   ##
=======================================
  Coverage   96.84%   96.84%           
=======================================
  Files           1        1           
  Lines          95       95           
=======================================
  Hits           92       92           
  Misses          3        3           

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