[documentation] #4055: Add ReadTheDocs config #3070

Job	Run time
Pull requests from forks should use other workflow	4s
pr_comment_reaction_rocket	0s
Check if github workflows were properly made from sources	19s
generate_matrixes	9s
prepare-macos-env	4s
prepare-windows-env	4s
Docker-iroha-builder	4m 3s
build-W	0s
build-UD (ubuntu gcc-10 Debug normal)	58m 38s
build-UR (ubuntu gcc-10 Release normal)	49m 14s
build-M (macos clang Debug normal)	2h 1m 53s
docker-R	0s
docker-D	0s
	3h 54m 28s

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