Add `bigdecimal` as a dependency #28

Job	Run time
cross-compile-linux	24s
cross-compile-windows (x64-mingw32)	54s
install-windows-native (2.7)	4m 7s
install-macos-m1 (2.7)	1m 14s
cross-compile-windows (x86-mingw32)	52s
install-windows-native (3.0)	1m 44s
install-macos-m1 (3.0)	58s
cross-compile-windows (x64-mingw-ucrt)	1m 0s
install-windows-native (3.1)	1m 43s
install-macos-m1 (3.1)	1m 1s
install-windows-native (3.2)	2m 8s
install-macos-m1 (3.2)	1m 47s
install-windows-native (3.3)	2m 33s
install-macos-m1 (3.3)	1m 16s
test-linux (2017, 2.7)	1m 37s
test-linux (2017, 3.0)	1m 17s
test-linux (2017, 3.1)	1m 24s
test-linux (2017, 3.2)	1m 31s
test-linux (2017, 3.3)	1m 11s
test-linux (2019, 2.7)	1m 25s
test-linux (2019, 3.0)	1m 16s
test-linux (2019, 3.1)	1m 22s
test-linux (2019, 3.2)	1m 14s
test-linux (2019, 3.3)	1m 14s
test-linux (2022, 2.7)	1m 25s
test-linux (2022, 3.0)	1m 11s
test-linux (2022, 3.1)	1m 12s
test-linux (2022, 3.2)	1m 19s
test-linux (2022, 3.3)	1m 15s
install-windows-ucrt (3.1)	1m 21s
install-windows-mingw (2.7)	3m 51s
install-windows-ucrt (3.2)	1m 25s
test-windows-mingw (2019, 2.7)	8m 54s
install-windows-mingw (3.0)	1m 29s
install-windows-ucrt (3.3)	2m 22s
test-windows-mingw (2019, 3.0)	5m 21s
test-windows-ucrt (2019, 3.1)	6m 1s
test-windows-ucrt (2019, 3.2)	7m 24s
test-windows-mingw (2022, 2.7)	8m 28s
test-windows-ucrt (2019, 3.3)	5m 47s
test-windows-mingw (2022, 3.0)	6m 2s
test-windows-ucrt (2022, 3.1)	6m 39s
test-windows-ucrt (2022, 3.2)	6m 19s
test-windows-ucrt (2022, 3.3)	8m 2s
	2h 0m 59s

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