Change README instructions to run all samples from root dir #801

Job	Run time
build-lint-test (3.12, ubuntu-latest)	5m 32s
build-lint-test (3.9, windows-latest)	6m 38s
build-lint-test (3.9, macos-arm)	7m 36s
build-lint-test (3.9, macos-intel)	7m 33s
build-lint-test (3.9, ubuntu-latest)	5m 27s
build-lint-test (3.12, windows-latest)	6m 16s
build-lint-test (3.12, macos-arm)	5m 24s
build-lint-test (3.12, macos-intel)	6m 28s
	50m 54s

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