Add doc images for auto-sharding #4275

Job	Run time
Build XLA / build	42m 57s
Build & publish docs	0s
GPU tests / test (benchmark_tests)	11m 52s
GPU tests / test (cpp_tests1)	21m 18s
GPU tests / test (cpp_tests2)	28m 57s
GPU tests / test (python_tests, xla_op1)	2h 11m 21s
CPU tests / test (benchmark_tests)	9m 59s
GPU tests / test (python_tests, xla_op2)	1h 19m 35s
GPU tests / test (python_tests, xla_op3)	1h 28m 40s
CPU tests / test (cpp_tests1)	15m 55s
GPU tests / test (python, torch_mp_op)	29m 46s
CPU tests / test (cpp_tests2)	17m 20s
CPU tests / test (python_tests, xla_op1)	17m 11s
CPU tests / test (python_tests, xla_op2)	9m 55s
CPU tests / test (python_tests, xla_op3)	11m 1s
CPU tests / test (python, torch_mp_op)	17m 29s
	8h 53m 16s

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