CI: 📝 👷 `make html` generate hierarchy graph #952

Job	Run time
rocq-core	41s
coq	43s
mathcomp-analysis-single	13m 11s
mathcomp-classical	2m 36s
mathcomp-reals	1m 56s
mathcomp-analysis	11m 33s
mathcomp-experimental-reals	1m 44s
mathcomp-reals-stdlib	1m 27s
mathcomp-analysis-stdlib	1m 36s
ssprove	5m 43s
	41m 10s

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