CMake

Add NaN propagation and array initialization notes to ?GEMM docs #801

Job	Run time
memory-check	9m 59s
test-install-cblas-lapacke-without-fortran-compiler	4m 50s
test-install-release (macos-latest, -Wall -Wno-unused-dummy-argument -Wno-unused-variable -Wno-un...	23m 29s
coverage	6m 48s
test-install-release (macos-latest, -Wall -Wno-unused-dummy-argument -Wno-unused-variable -Wno-un...	24m 10s
test-install-release (ubuntu-latest, -Wall -Wno-unused-dummy-argument -Wno-unused-variable -Wno-u...	9m 53s
test-install-release (ubuntu-latest, -Wall -Wno-unused-dummy-argument -Wno-unused-variable -Wno-u...	10m 59s
test-install-release (windows-latest, -Wall -Wno-unused-dummy-argument -Wno-unused-variable -Wno-...	14m 0s
test-install-release (windows-latest, -Wall -Wno-unused-dummy-argument -Wno-unused-variable -Wno-...	14m 22s
	1h 58m 30s

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