chore: add rackup gem #157

Job	Run time
test (2.7, ubuntu-latest)	37s
test-with-rack-2 (3.2, ubuntu-latest)	7s
test-with-active-support (2.7, ubuntu-latest)	29s
test-with-rack-2 (3.2, windows-latest)	2m 37s
test (2.7, windows-latest)	3m 15s
test-with-active-support (2.7, windows-latest)	3m 15s
test-with-rack-2 (3.2, macos-latest)	13s
test (2.7, macos-latest)	1m 46s
test-with-active-support (2.7, macos-latest)	1m 21s
test (3.0, ubuntu-latest)	32s
test-with-active-support (3.0, ubuntu-latest)	24s
test (3.0, windows-latest)	2m 47s
test-with-active-support (3.0, windows-latest)	2m 46s
test (3.0, macos-latest)	1m 15s
test-with-active-support (3.0, macos-latest)	35s
test (3.1, ubuntu-latest)	44s
test-with-active-support (3.1, ubuntu-latest)	18s
test (3.1, windows-latest)	3m 2s
test-with-active-support (3.1, windows-latest)	2m 30s
test (3.1, macos-latest)	52s
test-with-active-support (3.1, macos-latest)	35s
test (3.2, ubuntu-latest)	28s
test-with-active-support (3.2, ubuntu-latest)	22s
test (3.2, windows-latest)	4m 8s
test-with-active-support (3.2, windows-latest)	3m 4s
test (3.2, macos-latest)	51s
test-with-active-support (3.2, macos-latest)	55s
	39m 48s

Provide feedback