Add bun support #80

Job	Run time
test (ubuntu-latest, 2.7)	24s
test (ubuntu-latest, 3.0)	21s
test (ubuntu-latest, 3.1)	18s
test (ubuntu-latest, head)	13s
test (ubuntu-latest, jruby)	53s
test (ubuntu-latest, jruby-head)	56s
test (ubuntu-latest, truffleruby)	42s
test (ubuntu-latest, truffleruby-head)	1m 0s
test (macos-latest, 2.7)	55s
test (macos-latest, 3.0)	23s
test (macos-latest, 3.1)	40s
test (macos-latest, head)	45s
test (macos-latest, jruby)	1m 2s
test (macos-latest, jruby-head)	1m 27s
test (macos-latest, truffleruby)	2m 13s
test (macos-latest, truffleruby-head)	2m 10s
	14m 22s

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