example: specification of a left pad string padding function

[crodriguezvega]

This is a sample specification of a left pad string padding function. After addressing any feedback and merging this PR, I plan to open a PR to hwayne/lets-prove-leftpad to add it there as well.

• Tests added for any new code
• Documentation added for any new functionality
• Entries added to the respective CHANGELOG.md for any new functionality
• Feature table on README.md updated for any listed functionality

[crodriguezvega]

I've run make examples, but it seems to hang and the README.md doesn't get updated...

echo "<!-- DO NOT EDIT: THIS FILE IS GENERATED FROM examples/.scripts/README-text.md VIA 'make examples' -->" > examples/README.md
cat examples/.scripts/README-text.md >> examples/README.md
./examples/.scripts/run-examples.sh >> examples/README.md
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If you use programs that use GNU Parallel to process data for an article in a
scientific publication, please cite:

  Tange, O. (2025, February 22). GNU Parallel 20250222 ('Grete Tange').
  Zenodo. https://doi.org/10.5281/zenodo.14911163

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[bugarela]

I've run make examples, but it seems to hang and the README.md doesn't get updated...

This takes a few minutes to run, but it might be the case that you are hitting #1609

Don't worry, I can run this for you and update the dashboard