Start on GPU extensions #690

Job	Run time
Julia lts - windows-latest -	14m 46s
Julia 1 - ubuntu-latest -	16m 12s
Julia lts - ubuntu-latest -	13m 7s
Julia lts - macOS-latest -	10m 18s
Julia 1 - macOS-latest -	15m 16s
Julia 1 - windows-latest -	18m 6s
Julia nightly - ${{ matrix.os }} - ${{ matrix.arch }}	0s
	1h 27m 45s

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