[SR-15354] Update Render JSON spec with for new variant overrides property

[franklinsch]

Previous ID	SR-15354
Radar	rdar://83667105
Original Reporter	@franklinsch
Type	Task
Status	Resolved
Resolution	Done

Additional Detail from JIRA

Votes	0
Component/s	Swift-DocC
Labels	Task
Assignee	@franklinsch
Priority	Medium

md5: 46191424b60dc298cba237a4185e737f

Issue Description:

Update the render JSON schema with the changes introduced by #11

[franklinsch]

Opened a PR here: #20