Update to readme: #246

Job	Run time
rubocop	15s
Unit test (ubuntu-20.04, 3)	1m 44s
Unit test (ubuntu-20.04, 3.1)	1m 46s
Unit test (ubuntu-20.04, 3.2)	1m 44s
Unit test (ubuntu-20.04, 3.3)	1m 44s
Unit test (ubuntu-20.04, 3.4)	1m 50s
Unit test (ubuntu-20.04, jruby-9.4)	2m 29s
Unit test (ubuntu-20.04, truffleruby)	3m 46s
Unit test (macos-latest, 3)	1m 34s
Unit test (macos-latest, 3.1)	1m 43s
Unit test (macos-latest, 3.2)	1m 36s
Unit test (macos-latest, 3.3)	1m 47s
Unit test (macos-latest, 3.4)	1m 39s
Unit test (macos-latest, jruby-9.4)	1m 57s
Unit test (macos-latest, truffleruby)	2m 31s
Unit test (windows-latest, 3)	4m 26s
Unit test (windows-latest, 3.1)	3m 27s
Unit test (windows-latest, 3.2)	4m 7s
Unit test (windows-latest, 3.3)	4m 5s
Unit test (windows-latest, 3.4)	4m 54s
finish	0s
	49m 4s

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