add check for range parse result token matching input

[ijt]

This makes sure that we can always get the underlying substring that was parsed to get a date/time range.

[codecov[bot]]

Codecov Report

Merging #9 (2e048c7) into main (f4d7070) will not change coverage. The diff coverage is n/a.

@@           Coverage Diff           @@
##             main       #9   +/-   ##
=======================================
  Coverage   94.56%   94.56%           
=======================================
  Files           1        1           
  Lines         699      699           
=======================================
  Hits          661      661           
  Misses         22       22           
  Partials       16       16           

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