Update CHANGELOG.md (#764)

tagging HEAD of v2.20.2-nomad-1 at tgross's request

tagging HEAD v1.0.1-nomad at tgross's request

Merge pull request #710 from hashicorp/jbardin/marked-conditions

Better control of marks through conditional and for expressions

Merge pull request #707 from hashicorp/warn-on-duplicates-wrapper

Add functions to replicate old HCL V1 Behavior for backwards compatability

Merge pull request #704 from sarahalsmiller/check-for-duplicates

Update V1 Parser to Check for Duplicates

Merge pull request #694 from hashicorp/prepare-release-2.22.0

Prepare for v2.22.0 release

prepare for v2.21.0 release

Update CHANGELOG for 2.20.1

update CHANGELOG.md for v2.20