feat: add implementation of median for halfnormal distribution

[shubham220420]

Progresses: #9416

Description

What is the purpose of this pull request?

This pull request:

• This PR adds implementation of median calculation for half-normal distribution.

Related Issues

Does this pull request have any related issues?

This pull request has the following related issues:

• [RFC]: Tracking issue for complete implementation of @stdlib/stats/base/dists/halfnormal package #9416

Questions

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No.

Other

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No.

Checklist

Please ensure the following tasks are completed before submitting this pull request.

• Read, understood, and followed the contributing guidelines.

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[stdlib-bot]

Coverage Report

Package	Statements	Branches	Functions	Lines
stats/base/dists/halfnormal/median	$\color{green}169/169$ $\color{green}+0.00%$	$\color{green}8/8$ $\color{green}+0.00%$	$\color{green}2/2$ $\color{green}+0.00%$	$\color{green}169/169$ $\color{green}+0.00%$

The above coverage report was generated for the changes in this PR.

[Planeshifter]

Implementation is correct and PR is in good shape overall; thank you!

[shubham220420]

@Planeshifter the requested changes have been made, now I'll work on the variance part!

[Neerajpathak07]

@shubham220420 For future PR's on statistical distribution packages. Make sure to keep the PR title as:-

feat: add stats/base/dists/sub-package-name

For ex in this case it should be:- feat: add stats/base/dists/halfnormal/median

[shubham220420]

@shubham220420 For future PR's on statistical distribution packages. Make sure to keep the PR title as:-

feat: add stats/base/dists/sub-package-name

For ex in this case it should be:- feat: add stats/base/dists/halfnormal/median

will make sure working next time.

[shubham220420]

hey sir @Planeshifter can you review the changes whenever possible