Add .readthedocs.yaml file. #942

Job	Run time
build (linux-gcc)	13m 54s
build-containers (debian, debian, bookworm, x86_64)	12m 40s
build (linux-clang)	11m 59s
build (macos)	13m 39s
build-containers (fedora, fedora, 40, x86_64)	15m 3s
build (linux-i686-gcc)	13m 23s
build-containers (alma, almalinux, 9, x86_64)	14m 11s
build (android)	37s
build-containers (oracle, oraclelinux, 9, x86_64)	14m 2s
build (windows-cygwin-64)	15m 59s
build-containers (rocky, rockylinux, 9, x86_64)	14m 17s
build (windows-cygwin-32)	15m 15s
build-containers (ubuntu, ubuntu, noble, i686)	12m 57s
build (windows-msys2-64)	15m 11s
build (android-recovery, ubuntu-22.04, aarch64-linux-android32)	36s
build-containers (ubuntu, ubuntu, noble, x86_64)	13m 54s
	3h 17m 37s

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