Update PR checklist to also mention readme.md

[jdemelo]

This PR is to update the PR checklist to include mention of readme.md in addition to readme.html

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Please ensure your pull request (PR) adheres to the following guidelines:

• Please refer to our contributing documentation for any questions on submitting a pull request, link: Contribution Guide

Pull Request Checklist

Please check if your PR fulfills the following requirements:

• [ ] Testing of all the changes has been performed (for bug fixes / features)
• [ ] The readme.html has been reviewed and added / updated if needed (for bug fixes / features)
• [ ] Use the following format for the PR description: <App Name>: <PR Type> - <PR Description>
• [ ] Provide release notes as part of the PR submission which describe high level points about the changes for the upcoming GA release.
• [ ] Verify all checks are passing.
• [ ] Do NOT use the next branch of the forked repo. Create separate feature branch for raising the PR.
• [ ] Do NOT submit updates to dependencies unless it fixes an issue.
• [ ] Limit your pull request to one application and submit multiple pull requests if necessary.

  Pull Request Type

Please check the type of change your PR introduces:

• [ ] New App
• [ ] Bugfix
• [ ] Feature
• [ ] Code style update (formatting, renaming)
• [ ] Refactoring (no functional changes, no api changes)
• [ ] Documentation
• [ ] Other (please describe):

Release Notes (REQUIRED)

• Provide release notes as part of the PR submission which describe high level points about the changes for the upcoming GA release.

What is the current behavior? (OPTIONAL)

• Describe the current behavior that you are modifying.

What is the new behavior? (OPTIONAL)

• Describe the behavior or changes that are being added by this PR.

Other information (OPTIONAL)

• Any other information that is important to this PR such as screenshots of how the component looks before and after the change.

Pay close attention to (OPTIONAL)

• Any specific code change or test case points which must be addressed/reviewed at the time of GA release.

Screenshots (if relevant)

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Thanks for contributing!