support widening staticarray eltypes #607

Job	Run time
Documentation	1m 19s
Julia 1.6 - ubuntu-latest - x64 - push	2m 2s
Julia 1.6 - windows-latest - x64 - push	13m 16s
Julia lts - ubuntu-latest - x64 - push	1m 47s
Julia lts - windows-latest - x64 - push	2m 26s
Julia 1 - ubuntu-latest - x64 - push	4m 25s
Julia 1 - windows-latest - x64 - push	5m 14s
Julia pre - ubuntu-latest - x64 - push	3m 5s
Julia pre - windows-latest - x64 - push	3m 23s
Julia nightly - ubuntu-latest - x64 - push	4m 8s
Julia nightly - windows-latest - x64 - push	5m 6s
	46m 11s

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