Adds visualization and simple policy step to getting started docs on custom MARL env #1027

Job	Run time
tutorial-test (3.8, Tianshou)	3m 12s
tutorial-test (3.8, CustomEnvironment)	32s
tutorial-test (3.8, CleanRL)	5m 27s
tutorial-test (3.8, SB3/kaz)	4m 38s
tutorial-test (3.8, SB3/waterworld)	8m 31s
tutorial-test (3.8, SB3/connect_four)	3m 12s
tutorial-test (3.8, SB3/test)	4m 25s
tutorial-test (3.8, AgileRL)	10m 33s
tutorial-test (3.9, Tianshou)	3m 23s
tutorial-test (3.9, CustomEnvironment)	31s
tutorial-test (3.9, CleanRL)	5m 34s
tutorial-test (3.9, SB3/kaz)	6m 23s
tutorial-test (3.9, SB3/waterworld)	7m 53s
tutorial-test (3.9, SB3/connect_four)	3m 4s
tutorial-test (3.9, SB3/test)	2m 15s
tutorial-test (3.9, AgileRL)	9m 56s
tutorial-test (3.10, Tianshou)	3m 12s
tutorial-test (3.10, CustomEnvironment)	30s
tutorial-test (3.10, CleanRL)	7m 29s
tutorial-test (3.10, SB3/kaz)	4m 48s
tutorial-test (3.10, SB3/waterworld)	8m 9s
tutorial-test (3.10, SB3/connect_four)	3m 8s
tutorial-test (3.10, SB3/test)	2m 8s
tutorial-test (3.10, AgileRL)	11m 52s
tutorial-test (3.11, Tianshou)	3m 22s
tutorial-test (3.11, CustomEnvironment)	28s
tutorial-test (3.11, CleanRL)	7m 7s
tutorial-test (3.11, SB3/kaz)	4m 54s
tutorial-test (3.11, SB3/waterworld)	7m 55s
tutorial-test (3.11, SB3/connect_four)	2m 57s
tutorial-test (3.11, SB3/test)	3m 28s
tutorial-test (3.11, AgileRL)	11m 17s
	2h 42m 13s

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