Add Dependabot Configuration with Sync to 'dependentbotchanges' Branch

[Harmanpreet-Microsoft]

Motivation and Context

This PR introduces a new configuration for Dependabot and ensures that dependency updates are managed without disrupting the main branch.

Key Changes:
1.Added a dependabot.yml file:

Configured Dependabot to open pull requests targeting the dependentbotchanges branch for dependency updates.
This change allows for testing and validation before merging updates into the main branch.

2.Created a GitHub Action:

Ensures that changes in the dependentbotchanges branch are kept in sync with the main branch.
This helps maintain consistency between branches and prevents untested changes from breaking deployments.

Contribution Checklist

• I have built and tested the code locally and in a deployed app
• For frontend changes, I have pulled the latest code from main, built the frontend, and committed all static files.
• This is a change for all users of this app. No code or asset is specific to my use case or my organization.
• I didn't break any existing functionality 😄