[HTML] Add support for input and output files #815

Job	Run time
docker-master	1h 28m 43s
publish-standalone-dry-run	16s
test-standalone (master, dev, default)	1m 28s
build-js-of-ocaml (master, 4.11.1)	9m 8s
validate-docker-master	3m 0s
build-wasm-of-ocaml (master, 4.14.1)	19m 46s
standalone-haskell (master)	46m 33s
test-amd64	2h 15m 53s
generated-files (master)	22m 17s
deploy-js-wasm-of-ocaml	1m 21s
docker-check-all	7s
	5h 28m 32s

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