fix: ensure Node.js 12 compatibility

[wellwelwel]

Fixes #51.

---

Testing:

FROM node:12.22.12-slim

WORKDIR /app
COPY package.json /app/node_modules/sql-escaper/package.json
COPY lib /app/node_modules/sql-escaper/lib

CMD node --version && node -p "require('sql-escaper')"

Output:

v12.22.12
{
  dateToString: [Function: dateToString],
  temporalToString: [Function: temporalToString],
  escapeId: [Function: escapeId],
  objectToValues: [Function: objectToValues],
  bufferToString: [Function: bufferToString],
  arrayToList: [Function: arrayToList],
  escape: [Function: escape],
  format: [Function: format],
  raw: [Function: raw]
}

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Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (72fbc98) to head (6d0c4bc).
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Additional details and impacted files

@@            Coverage Diff            @@
##              main       #52   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            1         1           
  Lines          561       561           
  Branches       170       170           
=========================================
  Hits           561       561           

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