Merge pull request #24 from nobu/doc #91

Job	Run time
ruby-versions / Generate Ruby versions	2s
build (2.6 / ubuntu-latest)	20s
build (2.6 / macos-latest)	46s
build (2.6 / windows-latest)	3m 17s
build (2.7 / ubuntu-latest)	20s
build (2.7 / macos-latest)	39s
build (2.7 / windows-latest)	1m 17s
build (3.0 / ubuntu-latest)	9s
build (3.0 / macos-latest)	8s
build (3.0 / windows-latest)	1m 3s
build (3.1 / ubuntu-latest)	7s
build (3.1 / macos-latest)	16s
build (3.1 / windows-latest)	1m 4s
build (3.2 / ubuntu-latest)	7s
build (3.2 / macos-latest)	16s
build (3.2 / windows-latest)	2m 31s
build (head / ubuntu-latest)	5s
build (head / macos-latest)	12s
build (head / windows-latest)	1m 11s
	13m 50s

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