Update example in readme

[tpluscode]

I used @zazuko/env-node for simplest possible usage example

[changeset-bot]

🦋 Changeset detected

Latest commit: d1fbb08

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
rdf-validate-shacl	Patch

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[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (9d7ce9c) 98.88% compared to head (d1fbb08) 98.88%.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #119   +/-   ##
=======================================
  Coverage   98.88%   98.88%           
=======================================
  Files          12       12           
  Lines        1796     1796           
=======================================
  Hits         1776     1776           
  Misses         20       20           

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