Update readme with current `product-details` API #50

Job	Run time
Flake 8	17s
Python 3.7 + django22	17s
Python 3.7 + django32	15s
Python 3.8 + django22	15s
Python 3.8 + django32	18s
Python 3.8 + django40	18s
Python 3.9 + django22	20s
Python 3.9 + django32	20s
Python 3.9 + django40	19s
Python 3.10 + django32	18s
Python 3.10 + django40	23s
django-mozilla-product-details Release	0s
	3m 20s

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