Add working notebook with coupling flows [will later add splines as w… #558

Job	Run time
test (ubuntu-latest, 3.10, jax)	14s
test (ubuntu-latest, 3.10, numpy)	15s
test (ubuntu-latest, 3.10, tensorflow)	13s
test (ubuntu-latest, 3.10, torch)	14s
test (ubuntu-latest, 3.11, jax)	11s
test (ubuntu-latest, 3.11, numpy)	11s
test (ubuntu-latest, 3.11, tensorflow)	10s
test (ubuntu-latest, 3.11, torch)	9s
test (windows-latest, 3.10, jax)	12s
test (windows-latest, 3.10, numpy)	12s
test (windows-latest, 3.10, tensorflow)	12s
test (windows-latest, 3.10, torch)	12s
test (windows-latest, 3.11, jax)	12s
test (windows-latest, 3.11, numpy)	12s
test (windows-latest, 3.11, tensorflow)	14s
test (windows-latest, 3.11, torch)	12s
	3m 15s

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