docs: describe v2 targets and why they differ from V4.1

data: add test-v2 (part 7)

data: add test-v2 (part 6)

data: add test-v2 (part 5)

data: add test-v2 (part 4)

data: add test-v2 (part 3)

data: add test-v2 (part 2)

data: add test-v2

data: add train-v2 (part 9)

data: add train-v2 (part 8)

data: add train-v2 (part 7)

data: add train-v2 (part 6)

data: add train-v2 (part 5)

data: add train-v2 (part 4)

data: add train-v2 (part 3)

data: add train-v2 (part 2)

data: add train-v2

initial commit