use shorter extension names (#190) #631

Job	Run time
Documentation	1m 33s
Julia 1.6 - ubuntu-latest - x64 - push	1m 51s
Julia 1.6 - windows-latest - x64 - push	12m 14s
Julia lts - ubuntu-latest - x64 - push	1m 52s
Julia lts - windows-latest - x64 - push	2m 19s
Julia 1 - ubuntu-latest - x64 - push	2m 52s
Julia 1 - windows-latest - x64 - push	3m 34s
Julia pre - ubuntu-latest - x64 - push	3m 3s
Julia pre - windows-latest - x64 - push	5m 15s
Julia nightly - ubuntu-latest - x64 - push	4m 49s
Julia nightly - windows-latest - x64 - push	4m 55s
	44m 17s

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