Add HTML autoescape (#292) #321

Job	Run time
test-ubuntu-20.04-gcc-9	1m 10s
check-single-include	3s
test-ubuntu-20.04-gcc-11	1m 20s
test-ubuntu-20.04-clang-9	5m 38s
test-ubuntu-20.04-clang-11	1m 57s
test-ubuntu-20.04-clang-12	2m 4s
test-ubuntu-20.04-clang-11-no-exceptions	1m 41s
test-ubuntu-22.04-gcc	1m 28s
test-windows-2019-msvc	2m 13s
test-windows-2019-clang	1m 58s
test-windows-2019-gcc	1m 27s
test-windows-2022-msvc	1m 16s
test-macOS-12-gcc	1m 19s
test-macOS-12-clang	2m 40s
	26m 14s

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