Add iterators.md to docs index (#414) #872

Job	Run time
Documentation	1m 41s
Julia 1 - ubuntu-latest - x64 - push	12m 28s
Julia 1 - macos-latest - x64 - push	15m 5s
Julia 1 - windows-latest - x64 - push	13m 21s
Julia 1.6 - ubuntu-latest - x64 - push	6m 34s
Julia 1.6 - macos-latest - x64 - push	6m 52s
Julia 1.6 - windows-latest - x64 - push	16m 30s
Julia pre - ubuntu-latest - x64 - push	12m 14s
Julia pre - macos-latest - x64 - push	13m 19s
Julia pre - windows-latest - x64 - push	12m 49s
	1h 50m 53s

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