Add doxygen #84

Job	Run time
lint	9s
check_docker_files / check_docker_files	4s
build_base	0s
build (openmp, gcc, gcc, g++, -DKokkos_ENABLE_OPENMP=ON, native)	3m 7s
build (threads, gcc, gcc, g++, -DKokkos_ENABLE_THREADS=ON, native)	4m 31s
build (serial, gcc, gcc, g++, -DKokkos_ENABLE_SERIAL=ON, native)	3m 56s
build (cuda, nvcc, gcc, g++, -DKokkos_ENABLE_CUDA=ON -DKokkos_ARCH_AMPERE80=ON, native)	8m 13s
build (cuda, nvcc, gcc, g++, -DKokkos_ENABLE_CUDA=ON -DKokkos_ARCH_AMPERE80=ON, host_device, -DKo...	8m 19s
build (hip, rocm, hipcc, hipcc, -DKokkos_ENABLE_HIP=ON -DKokkos_ARCH_VEGA90A=ON, native)	7m 43s
build (hip, rocm, hipcc, hipcc, -DKokkos_ENABLE_HIP=ON -DKokkos_ARCH_VEGA90A=ON, host_device, -DK...	8m 41s
build (sycl, intel, icx, icpx, -DKokkos_ENABLE_SYCL=ON -DKokkos_ARCH_INTEL_GEN=ON, native)	12m 31s
build (sycl, intel, icx, icpx, -DKokkos_ENABLE_SYCL=ON -DKokkos_ARCH_INTEL_GEN=ON, host_device, -...	12m 41s
test (cuda, nvcc, self-hosted, cuda)	33s
test (openmp, gcc, ubuntu-latest)	49s
test (threads, gcc, ubuntu-latest)	49s
test (serial, gcc, ubuntu-latest)	49s
	1h 12m 55s

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