docs: improve example code of `stats/base/dists/triangular` namespace

[Tufailahmed-Bargir]

Resolves # .

Description

This pull request:

Add examples of the functions present in stats/base/dists/triangular namespace adds example demonstration using mean ,mode, median functions in the README.

Related Issues

resolve improve README examples of stats/base/dists/triangular namespace https://github.com/stdlib-js/stdlib/issues/1646

This pull request:

• resolves #1646

Questions

Sir the changes are correct??

Checklist

• [X] Read, understood, and followed the contributing guidelines.

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@stdlib-js/reviewers

[Tufailahmed-Bargir]

Sir please review this PR.