Make doxygen generate a spy.tag in the doc files #60

Job	Run time
msvc (Debug)	1m 11s
msvc (Release)	1m 11s
wasm (clang, wasm, Debug)	3m 12s
macosx (clang, x86_osx, Debug)	20s
clang-cl (Debug)	2m 11s
wasm (clang, wasm, Release)	3m 25s
macosx (clang, x86_osx, Release)	17s
clang (clang, x86, Debug)	2m 48s
clang-cl (Release)	2m 3s
clang (clang, x86, Release)	2m 52s
dpcpp (dpcpp, x86, Debug)	1m 14s
gcc (gcc, x86, Debug)	2m 44s
dpcpp (dpcpp, sycl, Debug)	1m 27s
nvcc	1m 13s
riscv (clang, rvv128, Debug)	2m 55s
gcc (gcc, x86, Release)	2m 47s
dpcpp (dpcpp, x86, Release)	59s
gcc (gcc, aarch64, -Wno-psabi, Debug)	2m 45s
riscv (clang, rvv128, Release)	3m 1s
gcc (gcc, aarch64, -Wno-psabi, Release)	2m 50s
dpcpp (dpcpp, sycl, Release)	1m 19s
gcc (gcc, aarch64.sve, -Wno-psabi, Debug)	2m 51s
gcc (gcc, aarch64.sve, -Wno-psabi, Release)	2m 49s
gcc (gcc, aarch64.sve2, -Wno-psabi, Debug)	2m 48s
gcc (gcc, aarch64.sve2, -Wno-psabi, Release)	2m 44s
gcc (gcc, ppc64, -Wno-psabi, Debug)	2m 47s
gcc (gcc, ppc64, -Wno-psabi, Release)	2m 49s
	59m 32s

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