Add Datadog Synthetic tests workflow

[JohnDaWalka]

This workflow triggers Datadog Synthetic tests on push and pull request events to the main branch.

Description

Please include a summary of the changes and be sure to follow our Contribution Guidelines.

Type of change

• 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:

• I have selected the correct base branch.
• I have performed a self-review of my own code.
• I have commented my code, particularly in hard-to-understand areas.
• I have made corresponding changes to the documentation.
• My changes generate no new warnings.
• Any dependent changes have been merged and published in downstream modules.
• I ran npm run test and my test cases cover all the lines and branches of the added code.
• I ran npm run build with success.
• I have tested my code on the live network.
• I have checked the Deploy Preview and it looks correct.

[Copilot]

Pull Request Overview

This PR adds a new GitHub Actions workflow to automatically trigger Datadog Synthetic tests when code is pushed or pull requests are opened against the main branch. This enables automated end-to-end testing as part of the CI/CD pipeline.

• Adds GitHub workflow configuration for Datadog Synthetic test execution
• Configures workflow to run on push and pull request events to main branch
• Sets up authentication using GitHub secrets for Datadog API access

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