Relay spec: Relay Classic, Relay Legacy, and Relay Modern meanings

[sonatard]

The following spec mentions Relay Classic, Relay Legacy, and Relay Modern. Are the specifications that each of these refers to documented? or if they have already been deprecated, which one is currently valid?

It would be helpful if the meaning of each of those could be clarified.

relay/website/spec/Connections.md

Lines 377 to 381 in 12965ce

	NOTE As this spec was created with Relay Classic in mind, it's worth noting that
	Relay Legacy did not define `startCursor` and `endCursor`, and relied on
	selecting the `cursor` of each edge; Relay Modern began selecting
	`startCursor` and `endCursor` instead to save bandwidth (since it doesn't use any
	cursors in between).