Add release notes for 6.0 (#2625)
Add release notes for 6.0 (#2625)

* [WIP] Add release notes for 6.0

* Apply suggestions from code review

* Add item about permanence of upgrade to 6.0

* Continue adding items from changelogs to release notes

* Update after sync mtg

* Update content/sensu-go/6.0/release-notes.md

* Update content/sensu-go/6.0/release-notes.md

* Update content/sensu-go/6.0/release-notes.md

* Add other js functions and Docker env vars

* Update release date

* Add links for new JS functions and SQE

* Remove commercial designation from SQE

* Add draft synopsis

* Add Postgres/GraphQL fix to 6.0 release notes

* Update content/sensu-go/6.0/release-notes.md

* Update content/sensu-go/6.0/release-notes.md

* Update content/sensu-go/6.0/release-notes.md

* Apply suggestions from code review

* Update content/sensu-go/6.0/release-notes.md

* Apply suggestions from code review

* Apply suggestions from code review
sensu/sensu-docs,sensu/sensu-docs,sensu/sensu-docs,sensu/sensu-docs,sensu/sensu-docs