Add a pull request template

[Benjamin-Nussbaum]

Description

Add a pull request template to standardize PR descriptions, including sections for Description, Motivation and Context, Testing, Screenshots, Types of changes, and Checklist. The template guides contributors to provide necessary information for review and QA.

Motivation and Context

This template improves contribution quality by ensuring PRs include clear purpose, testing details, and change classification. It reduces back-and-forth during review and makes it easier to track which issues are addressed.

How have these changes been tested?

• This template is based on https://github.com/stevemao/github-issue-templates/blob/master/questions-answers/PULL_REQUEST_TEMPLATE.md?plain=1
• This template is located in .github/PULL_REQUEST_TEMPLATE/pull_request_template.md as specified by https://docs.github.com/en/communities/using-templates-to-encourage-useful-issues-and-pull-requests/creating-a-pull-request-template-for-your-repository

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist:

• My code follows the code style of this project.
• My changes require a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing tests passed.

[SoroushHoseini]

Looks useful to me