Add capitalize function #310

Job	Run time
check-single-include	3s
test-ubuntu-20.04-gcc-9	1m 15s
test-ubuntu-20.04-gcc-11	2m 24s
test-ubuntu-20.04-clang-9	3m 20s
test-ubuntu-20.04-clang-11	2m 47s
test-ubuntu-20.04-clang-12	3m 1s
test-ubuntu-20.04-clang-11-no-exceptions	2m 41s
test-ubuntu-22.04-gcc	1m 24s
test-windows-2019-msvc	48s
test-windows-2019-clang	2m 20s
test-windows-2019-gcc	2m 33s
test-windows-2022-msvc	1m 17s
test-macOS-11-gcc	5m 45s
test-macOS-11-clang	7m 22s
test-macOS-12-clang	3m 55s
	40m 55s

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