Add changelog file

[kinow]

Is your feature request related to a problem? Please describe.
Add 1.0.0, and 1.1.0 release notes as well, and prepare for 1.2.0.

Describe the solution you'd like

Describe alternatives you've considered

Additional context

Notes

1. Check the Troubleshooting Guide in the wiki.
2. Ask in the Gitter Chat Room - please do not submit issues for support requests.
3. Use the GitHub Issue Search to check if the issue has already been reported.