DOC: README.rst: note about pytest support #37

Job	Run time
on ubuntu-latest machine - Python 2.7	5s
on ubuntu-latest machine - Python 3.7	25s
on ubuntu-latest machine - Python 3.8	23s
on ubuntu-latest machine - Python 3.9	32s
on ubuntu-latest machine - Python 3.10	28s
on ubuntu-latest machine - Python 3.11	25s
on macos-latest machine - Python 2.7	11s
on macos-latest machine - Python 3.5	1m 17s
on macos-latest machine - Python 3.6	1m 18s
on macos-latest machine - Python 3.7	31s
on macos-latest machine - Python 3.8	37s
on macos-latest machine - Python 3.9	7m 8s
on macos-latest machine - Python 3.10	38s
on macos-latest machine - Python 3.11	46s
on windows-latest machine - Python 3.5	2m 21s
on windows-latest machine - Python 3.6	1m 55s
on windows-latest machine - Python 3.7	1m 23s
on windows-latest machine - Python 3.8	1m 2s
on windows-latest machine - Python 3.9	1m 1s
on windows-latest machine - Python 3.10	1m 5s
on windows-latest machine - Python 3.11	1m 16s
on ubuntu-20.04 machine - Python 3.5	36s
on ubuntu-20.04 machine - Python 3.6	49s
	26m 12s

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