adding changelog for 1.6.0 release

[shenda1]

Description

PR is raised to update readme/changelog for release v1.6.0

ISSUE TYPE

• Docs Pull Request

# Checklist:

- [ ] I have performed a self-review of my own code to ensure there are no formatting, vetting, linting, or security issues
- [ ] I have verified that new and existing unit tests pass locally with my changes
- [ ] I have not allowed coverage numbers to degenerate
- [ ] I have maintained at least 80% code coverage
- [ ] I have commented my code, particularly in hard-to-understand areas
- [ ] I have made corresponding changes to the documentation
- [ ] I have added tests that prove my fix is effective or that my feature works
- [ ] I have maintained backward compatibility


# How Has This Been Tested?
Please describe the tests that you ran to verify your changes. Please also list any relevant details for your test configuration

- [ ] Unit tests
- [ ] Acceptance tests

[shenda1]

e2e pass

[gokul-srivathsan]

LGTM

[shenda1]

e2e pass