README updates, esp for example #725

Job	Run time
changes	8s
run-deny	1m 27s
run-checks (ubuntu-latest, stable)	1m 4s
run-docs	4m 53s
run-checks (ubuntu-latest, nightly)	2m 33s
run-tests (ubuntu-latest, stable, all)	12m 44s
run-tests (ubuntu-latest, stable, none)	7m 59s
run-tests-windows (stable, all)	17m 46s
run-checks (macos-latest, stable)	2m 5s
run-tests-windows (stable, none)	8m 13s
run-checks (macos-latest, nightly)	5m 14s
run-tests (ubuntu-latest, nightly, all)	10m 39s
run-tests-windows (nightly, all)	20m 48s
run-checks (windows-latest, stable)	4m 12s
run-tests (ubuntu-latest, nightly, none)	7m 48s
run-tests-windows (nightly, none)	15m 44s
run-checks (windows-latest, nightly)	7m 24s
run-tests (macos-latest, stable, all)	4m 55s
run-tests (macos-latest, stable, none)	6m 33s
run-tests (macos-latest, nightly, all)	15m 37s
run-tests (macos-latest, nightly, none)	12m 59s
	2h 50m 45s

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