Add a new "yarn release-notes" script to generate release notes

[anupriya13]

Description

Type of Change

Automate release notes creation by adding a new yarn script

Why

To save us some time when generating release notes. Before created it as a github workflow but now moving it to a local script.

Refer #14675 for context

Steps to follow

1. Set up your personal access token

• Go to GitHub and log in: https://github.com/
• Click on your profile picture (top-right corner), then click Settings
• On the left sidebar, click Developer settings
• Then click Personal access tokens > Tokens (classic)
• Click Generate new token > Generate new token (classic)
• Give it a name like "Release Notes Script"
• Set an expiration (choose less than 90 days)
• Under Scopes, select the permissions your script needs. For fetching commits and repo info, you typically need:
  repo (full control of private repositories)
  or at least repo:status, repo_deployment, public_repo (for public repos)
• Click Generate token
• Find the token you're using (whichever token you created).
• You should see a message or option to "Grant access to your organization" or "Authorize SAML SSO" for your token.
• Click that button to authorize the token with the organization.
• Copy the generated token

2. Set env variables at root of the repo

set GITHUB_TOKEN=<your-personal-access-token>
set RELEASE_TAG=0.79.0
set START_DATE=2025-05-06
set END_DATE=2025-05-30

3. Run "yarn release-notes" at the root of the repo

4. You will see a release-notes.md file generated at packages@rnw-scripts\generate-release-notes\release_notes.md which will have all the data you need.

Screenshots

Testing

Tested locally

Changelog

Should this change be included in the release notes: NO

Add a brief summary of the change to use in the release notes for the next release.