Add AWS CodeCommit examples for push request and also README to configure AWS CodeCommit

[savitaashture]

Changes

Add README and samples to integrate triggers with AWS codecommit

Submitter Checklist

As the author of this PR, please check off the items in this checklist:

• [ ] Has Docs if any changes are user facing, including updates to minimum requirements e.g. Kubernetes version bumps
• [ ] Has Tests included if any functionality added or changed
• [ ] Follows the commit message standard
• [ ] Meets the Tekton contributor standards (including functionality, content, code)
• [ ] Has a kind label. You can add one by adding a comment on this PR that contains /kind <type>. Valid types are bug, cleanup, design, documentation, feature, flake, misc, question, tep
• [ ] Release notes block below has been updated with any user facing changes (API changes, bug fixes, changes requiring upgrade notices or deprecation warnings). See some examples of good release notes.
• [ ] Release notes contains the string "action required" if the change requires additional action from users switching to the new release

Release Notes

NONE

[savitaashture]

@dibyom PR is ready to review PTAL Thank you

[tekton-robot]

[APPROVALNOTIFIER] This PR is APPROVED

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