Add `--print-characters` command #76

Job	Run time
minimal-versions	56s
build-and-test (ubuntu-latest, stable)	1m 33s
build-and-test (ubuntu-latest, beta)	40s
build-and-test (ubuntu-latest, nightly)	41s
build-and-test (ubuntu-latest, 1.79.0)	42s
build-and-test (macos-latest, stable)	57s
build-and-test (macos-latest, beta)	43s
build-and-test (macos-latest, nightly)	46s
build-and-test (macos-latest, 1.79.0)	46s
	7m 44s

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